Sonic Riders X-Treme : Cosmo

Cosmo's not an official character because Sonic X is non-canon. In the games continuity, Cosmo never existed (although Void looks similar to Cosmo). So since Sonic X is a separate continuity from the games, any character introduced in Sonic X (Chris, Chuck, Metarex, Cosmo, Dark Super Sonic, etc), is considered non-canon to the games.

Now to comment on the actual art itself: The pose and the perspective in this aren't bad, the outlines seem a little too thick, but the character design fits the Sonic Riders theme pretty well. And I like the logo.