My sister wanted a drumset done as a desktop image and here it is. I’m happy with the result but I’ve never been good at criticising 
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Well, turn OSA on for starters.
The lighting is poor. It doesn’t light the focus of the scene (the drumkit) very well, and the harsh shadows look extremely unrealistic. Try using area lights or buffered spots instead.
With these changes the drumkit will be visible enough to start critting…
Alex
Something like this?
I think it made the crome look a little dim but maybe it’s just me.
Ok, next step is to add more lighting (or, if you are feeling adventurous, press the AO button in world settings). By more lighting I mean another lamp or spot from another direction.
Next, camera angle needs to be lowered (this is an opinion).
Next, select the objects, press F9, press set smooth and turn on auto smooth (to make the drums, cymbols look rounder).
Then someone who knows about drums can crit you 
This can become a really neat background if you do some little additions
- start using the smooth button and Subdivision to make the faces of the drum cylinders disapear (unless you want it that way)
2)Read on 3 point lighting. Here is a quick summary. 1 Shadow castin spotligh, 1 lamp directly where the camera is (so there are not completely dark spots in your image) and 1 light for ( i can never remember) something like more lighting in the back
- do a neat bright white material for the ground. A white marble floor with some reflection and bump map would really add a nice effect and make the desktop more pleasing to look at
Continue!
you should make the tripods under the snare and the discs bigger
You have a good base to improve on. Aside from the above mentioned smoothing and lighting issues:
Switch the position of the crash and hi-hat (doubled) cymbals. The hi-hat is always next to the snare drum (the lone drum on a tripod stand) and is played with the left foot and right hand by most drummers (it should have a pedal mechanism, which you may have, but I can’t see it). You also need to model the clamp holding the topmost cymbal of the hi-hat, otherwise it won’t go up and down with the pedal… hehey.
It’s hard to tell wether the two rack toms are of different diameter but they should be. In basic kits they are usually 8" and 10" or 10" and 12". They should be a bit deeper as well.
The floor tom should be even larger than the largest rack tom. It’s hardware looks a tad too bulky.
Keep those render coming!