I began working on this shortly after the competition began and have done everything I can think of to make it look good, however it still does not look right to me… Does anyone else know what I mean? is it the shaders or lighting or something? anyways please critique anything about the picture and suggest how I can make the materials more realistic and advice on post processing or anything else…
Interesting idea. Is there a reason that all the characters are “un-posed”? The two at the bottom are presumeably toiling away at some forced labour? In which case, it would tell more of a story if they look like they are doing something, and pained expressions should help complete that story! Sweat on the brow… You could probably fit another slave type character on the right, and have him out of focus. I would probably try to go for a bit more of an industrious look to that whole area (i.e. it’s really being used, and the mean santa characters are forcing them to work). Depending on how busy you want it to look, how much space you have, and how it affects the composition of the image - you could add a few more things going on down there. Perhaps space for one of the left facing to the right?
Regarding the industrious look - I don’t know your intended story, but I would try and find a way to add a furnace or something similar to the left of the image (where those orangy-gold looking door things are). Obviously that would have to fit in with what your characters are doing, but I am envisaging a hot orange glow throwing light throughout the scene…it could add lots of interesting highlights and would provide a nice contrast to any blue-ish light from outside. That suddenly reminded me of a magazine cover (more than 20 years ago…can’t find it now!) that was for lemmings on the ZX spectrum (haha) and it captured the fear on the lemmings faces perfectly - there was an orange light from some fire, and a darker blue glow from the other side…and highlighted sweat/fear on the lemmings faces lol…anyway, I think that is roughly what I had in mind.
Repeating textures - the wooden plank on the wall at the right is clearly repeating for all 7 planks, try and prevent that. The planks to the left of those look better (more variation).
Textures on the brick pillars - some appear to be rotated (see the two either side of the santa type character). Perhaps some kind of subtle bump map and/or a displacement map would help add a little depth to those brick areas.
Snow flakes in background seem a bit large, but that is your choice with your artistic vision. I would probably try and make it look more like a blizzard outside (take a look at how this might be done with rain to get the motion blur). Maybe a subtle fog outside would help add to the cold look.
Are those chimneys in the background? If so, then you gotta put smoke on them somehow! 
The floor is very clean at the bottom. Depending on what the purpose of that room really is, you could add some randomly placed objects with the particle system. Maybe even a rat or something to make it seem a bit dirtier down there
You could try a slightly shorter focal length on your camera too, you may find that it provides a nicer perspective and helps give you a little more space to make the scene look more industrious (if you want to do that). Only do that if it actually helps of course, sometimes it’s hard to tell without actually playing with the scene.
Anyway, it’s your idea and work - so take all comments with a grain of salt, obviously everyone would approach it differently, so ignore any or all of it. 
In my opinion it is the lifelessness of the characters that detract, we need to feel / see something from them. Also probably move evil Santa from directly above the minion below, maybe place 'em on either side of the right hand sides third line?
thank you for all the advice… I like the idea of the furnace, yes i was going for a factory look and those are chimneys… but i can’t make smoke for some reason. Also the brick textures do have normal mapping however it does not look as realistic as it should… anyone know why?
about the characters, I was originally going to have them posed in that way, however I had to render them seperately because I wanted to have SSS on the skin, which is only supported in CPU rendering, and rendering the entire scene in CPU would take too long so the characters are image planes with alpha backgrounds, resulting in limited character interaction.
I will try and solve this problem but in the meantime does anyone know how I can improve the shaders/compositing/camera position? and how do I make the snow more realistic? I am planning to improve this image a lot despite the contest being over, because it fits with a short film/game idea I had a while ago… I will try and make realistic characters and better lighting. What do you think of the current lighting setup? I agree with having more contrast/colours but would it be a good idea to use a HDR as well as mesh lights?
There are tutorials for smoke, so you should be able to get it to work. I don’t know if you can do it in Cycles yet, but at worst you could do it in BI and then composite into the cycles render. Alternatively you could skip the compositor and just use your own technique of planes with alpha backgrounds. You can render the smoke separately in the same scene and make sure that you export it with alpha transparency. You could add a gentle wind force to make it interesting…and a very gentle red glow in the chimney…I have seen that before in a tutorial on YouTube…those kind of touches can bring an image to life. A quick google search shows one that I remember (“Smoke simulation in cycles - blender 2.62”), it has the glow I was talking about.
I don’t know what the issue is with the bricks, but I suspect that the normal mapping is not right. If your normal map is storing normals that tell the renderer that a particular part of the image has a normal in a particular direction, then that is probably going to be wrong on all those parts where your texture is rotated 90 degrees. I don’t want to spread misinformation, but I have recently begun to understand that a lot of normal mapping that people do is inappropriate. As I understand it, typically normal maps should be baked from an existing 3D model, and then used on that same 3D model. First thing you need to do is to unwrap your surfaces correctly so that the textures are aligned the right way up (you can check which vertex is corresponds to which vertex on the UV unwrap…so do check this!), and then you can work on getting the right effect on the surface. I would probably put a fine mesh on the pillar and use a displacement map…the reason for that is because you can see the edges of all the pillars (12 edges!), and no normal mapping or bump mapping is ever going to give you a pretty silhouette. If you do that, you will start to see the bricks shape in the silhouette. I think that will look a lot better. You should probably try and use different textures at the top of the pillars, and perhaps on the wall at the back. The black brick texture just looks a bit overused.
Regarding the characters…scrap the SSS and use the GPU rendering. The SSS is pretty much invisible in this render, and the image would benefit much more from pose-able characters.
Regarding current lighting, I would prefer more contrast, but that is personal preference. Right now it looks a bit even in value, my eyes aren’t drawn to any particular part of the image. Try putting in the orange light for the furnace and turn down the rest of your lighting to see what you get. Note: the light from a furnace would be slightly recessed from the edge of the furnace, so the light would probably be light a fairly soft edge rectangular spot lamp. I recall trying that once when I was modelling a train with a furnace and I it was quite noisy trying to model the actual furnace geometry with recessed light…so maybe try a spot lamp, experiment! The furnace will an obvious focal point, and it may help you decide on the composition.
HDR environment lighting might work, but it might end up giving you a little less control over the lighting within the scene. If you make a node set up to allow you to adjust the influence the HDRi environment lighting has on your scene, then it may be worth trying.
There is something about the lighting that doesn’t seem correct. Is there a moon that is the source? Are there lights illuminating the interior of this structure?
I would also suggest adding tools to the work benches - details.