I did some art for a TMNT cover a while back. It will appear on issue #35 (out in June, I think). I don't plan on doing much more work on licensed characters, but the turtles are an exception. Eastman & Laird's original TMNT was (and is) a huge inspiration for me.
...and here's an alternate color version of the cover (which I prefer).
Also, the collected PLANETOID Vol. 1 is now available on Amazon.