The art looks OK but you might want to play around with some other designs. I would also suggest adding a texture to the background to make it look a little more professional. As far as the buttons I would suggest grouping the player1 start with the player 1up on the left top of the CP and the player 2start and 1up on the right top (sort of above the controls for those players. Then I would place the esc, enter, pause buttons in the middle. I would also add one more button to that group like a tab button for emulator control. Not sure if your not wanting a trackball but that would be something to consider as well.