Hello,
This is my first time doing a type of Archviz interior.
I know that something is off but i can’t tell what. Some materials are not good like the one on the chimney for example.
But i’m mostly here for render and lighting advice.
Thanks everyone 
Seems you have 2 lightsources outside the house. For realism you should only have one. I would ditch the one casting shadows behind the couch.
It also seems it’s early afternoon, so it’s logical that the main window is facing south, where the sun is.
Indeed i have 2 lightsources, otherwise the left part of the room would have been very dark.
Should i just increase diffuse light bounces to counter that ?
What stands out to me are some of the textures. For example the brick wall. You may need to soften the normal/bump as it looks strange to me. I think this is also a problem with the couch texture (which is seems to low a scale - the threads are massive), and the sacatter cushions. There are plenty of good free textures (e.g. even the free ones on Poliigon would work) so worth trying. You can have great lighting but without appropriate textures the scene will always look like early CGI.
The rug would also benefit from more fibres as it looks very sparse and you can see gaps. Even if that is realstic to the product, on render it looks strange. Personally, I’d change the style of rug to a more shorthair version so you can avoid the various issues that come with particle setups.
My personal taste, but the plant on the window is redundant. Feels off balance and adds eye clutter.
You might also get a more realistic approach if you use the sky texture node rather than HDRI. Crank up the brightness of the background node - I often find anything from 3 to 30 is required. I also use 20-32 light bounces most of the time. Anywhere from 1000 to 4000 samples might be required.
The look unavoidably depends on the models themselves. The sofa, chair and carpet models are not particularly realistic so that makes the overall image look not as good. It’s quite tricky to model soft furniture realistically. In Blender you can do that using cloth simulation and cloth brushes. Cloth brushes are quite a fast way to get reasonable results(relatively, don’t expect 15minute results), but it is still hard to achieve the detail and subtlety of the look one can get with cloth simulation like in Marvelous Designer. It is definitely possible though, but requires a lot of time and skill that you can only get through practice.
Alternatively you could just use made models that you can find online or buy. Some furniture manufacturers do provide 3d models for their products, but usually they are not very high quality. In recent years the situation is slowly improving and in some cases one might get pleasantly surprised with the quality of manufacturer provided models as well. It’s not super common still, but way way better than it used to be a few years ago. To give some random example www.ditreitalia.com have a 3d configurator for some of their products that you can download. They are not amazing, but often still might be useable. This is just a random example that I happen to remember, there are a lot of others. You can find furniture models online free or for a price, but they are often way cheaper than the time you will spend if you want to model them yourself.
The carpet you have needs more work.
You could make light more realistic. light coming from outside is around 6500K and artificial sources are 3000-4000K, so the light form outside pretty much always is a lot cooler than warm artificial light. Gradients in light(one part of the room being lighter than some other) may add more feeling of depth. Using gobos for sunlight to make it have some tree shadow might improve the look a lot. There is something very recognisable about tree shadows. Look at the shadow coming from the window:
That’s technically a very cheap effect that requires very little work and time, but it adds a lot of value visually. Something about the shadows looks way more realistic than it would with plain light.
Thanks a lot for all your answers, it means a lot to me.
I will try to improve some stuff like you said when i have some freetime.
I had trouble creating this carpet (first time using hair particle)
And thanks a lot for the lighting insight. Using gobo and changing the Kelvin value can help a lot too.
I’ll keep you updated, and i’m keeping all that in my mind for futur render.
I have seen many renders with completely unrealistic white light and I think they can look very nice as well. Personally though I prefer to have some realism in the light. I often do not go all the way and have artificial light a lot cooler than it would be in reality, because I find realistic strong color contrast in the light might be distracting in some situations and also photographers adjust white balance when taking photos accordingly, so we don’t see particularly yellow interior photographs often and it might seem unusual. I think it’s something like 4500K in my example render and outside is HDR so around white - 6500K. So, it’s not a rule, the way I see it, but it’s definitely a tool worth considering. I mean it can be a rule, if you make it so, but I think it doesn’t have to be.
Also some places, you can find free furniture models: https://zeelproject.com/, https://blendermarket.com/, https://sketchfab.com/, https://www.blendswap.com/.
Sometimes furniture selling websites may have browser 3d configurators that do not allow downloading the model, so you can hit F12 on Chrome or Firefox and probably other browsers to go into developer mode, and at the Network tab, you will find resources that are downloaded while loading the page and you might find 3d models loaded in GLB format there often, so you can get it. This might of course be breaking copyright laws in some cases, so that’s up to you to find out. By the same logic, interior designers break the same laws just downloading product photographs and showing them to their clients at the same time making the sellers profit, so… I am not sure, how copyright laws work here exactly… But they exist.
A more pragmatic thought… which may affect the perception of the scene… before even adding more “detail”…
If the room has this kind of windows (big and above the TV) then i guess someone should have somekind of curtain ir shutters to be able to see someting on the TV… also the seems to be “fixed”… ?? No window handle to open them… ??
You may call this “essential pragmatic” details… and… where is the TV-remote ?? 
