I've been practicing my digital rendering. I could use some pointers probably, but here's my Mach 5 with Speed tucked into the side panel on a turn. *G*

http://i237.photobucket.com/albums/ff72/onemodelcitizen/digitalspeed.jpg

Overall, its a nice start. Only thing I can point out at this time is your lineart. Some lines could of been erased. Like the ones that separates your shadows with reflections...
Keep practicing !

Justin.