The first thing that jumps out is the inconsistent outlining....you've got outlines on some stuff, and not on others--pick one or the other.
The next thing that's rather bothersome is the lack of a light source...I mean, if you look close you can tell that there's some subtle shading, but personally, I'd try to be much more drastic.
Another thing that sticks out is that everything feels very flat and square--add some life to it man! Don't be afraid to use lines that don't line up with the isometric plane...curvy lines are your friend, as you can see on what you've kind of got going on the chair.
Lastly, I think the computer (its a computer right?) could use quite a bit of work. I'd spend some time and make it look more computer-y if I was you.
As for the carpet, I'd ignore the dither pattern and go for more of an edge thing--I mean, if it's like a shaggy carpet, show frillies around the edge of the room and objects, but if it's a flat carpet, I think you'll be just fine with what you've got...as long as you incorporate some more apparent shading.
Good luck man.
