Admin buttons:
If you plan on having exit and reset buttons, I'd move them away from the other buttons. You don't want to hit them by accident in the middle of a game when you mean to press a different button.
Also, why the up, down, left and right buttons?
Artwork:
Font and background are nice. So is the character art, but obscuring faces and/or hands is generally a bad idea when it comes to figures. At the very least, I would move Raph up a bit, so his chin isn't covered by a button. But I'd also try to reposition Michelangelo and Leonardo as well, to try to avoid covering their hands by joysticks.
I also recommend incorporating some sort of border or shaded area around the button and joystick areas. This helps tie the controls into the underlying artwork, as opposed to having them look like they are "floating" above it.
Overall, it's a good start, but with tweaking it could be quite stellar.