I saw a pic of the film version of Casey Jones, and its definately interesting. He's sleeker and less bulky than he is from the 2003 cartoon, and his design reminds me a little of Marvel's Night-Thrasher. I hope he'll get some cool moments in this film. He's my favorite human TMNT character.
What's wrong with Marc Thompson's Casey Jones from the 2003 series? I though he sounded fine. He has a little bit of a "Nu Yawk pug" sort of accent going, but it seems to fit Casey to me. And it was different than Pat Fraley's "Clint Eastwood" impersonation of Casey from the original series.
We'll see when Flynn brings to the role.
I agree that it would have been cool if Elias Koteas reprised the role of Jones for a voiceover. I always felt his Casey, least circa the 1990 film, is rather underrated in the "geek circles".