Your colors and shading is really quite marvelous, and the quality of your actual lines is pretty good.

On the other hand, you definitely need to work on your sense of depth, perhaps do some practice with vanishing points.

On top of that, your characters come off stilted, even stiff. The best way to address this is to go out in public on a sketch crawl, drawing people you see. It's a good way to rid yourself of any hesitation/lack of commitment in your lines- instead of constantly hitting Undo for the "perfect" line for a given form. In addition, you'll find it a simpler feat to bring the personality and story out in your characters when you've already been capturing it in your daily people sketches.

Basic, basic stuff I'm suggesting, but it will bring your work to the next level