The VG Resource

Try looking here: http://ssn.sonicstadium.org/tutorials/sp/basics/home
This is The Sonic Stadium's Sonic Spriters Network tutorial page for spriting basics. Perhaps here there'll be something that'll help you improve?

Update!
Gave him the correct eye color, purple. Was confused by the not-Fang in Miles's avatar.
Also added a new move, Pirouette. Can be a dash attack, can be an areal attack, you decide.

@Miles: The link does not work for me.

Added his machine, the Marvelous Queen.

EDIT:
Tweaked his running animation:

Really? Well, the link works fine for me...

About the running animation... The hands need to be a bit more mobile, the tail doesn't seem right, and the head is still small. Plus, his stepping looks like it's in a {da-dum, da-dum} rhythm. It just seems off.