Good start, but you need to pay more attention to the detailing.

Needs alot of highlight and shading work, but it's a foundation to start with.

Here's one I did awhile back, take a look at the highlight and shading technique:

http://img246.imageshack.us/img246/9626/spritetc3.gif

It's a good start though, just work on adding some depth and flesh it out.

I'd say you're on the right track :)

Shade, depth and the all important whatever... That depends on style and "school". I've seen some pretty awesome drawings that are very flat indeed, with no or little details. What you could do, is to decide on what style you want: You want that nitty-gritty detail stuff or the simple approach? Then, pursue that decision.