First, I really like the detail work for the joysticks and buttons, especially the Missile Command buttons and Karate Champ detail.
What really throws this off plain blue gradient without any texture. In Photoshop you can either add some noise and do a motion blur, or render clouds, or SOMETHING so we don't have just BLUE GRADIENT. The Galaga logo also doesn't seem to "go" with the theme with Karate Champ, it just seems stuck on there. Also, the orange border doesn't match anything else on the CP. Does this color appear on the cabinet? YELLOW is the complimentary color to blue, so I would go with a Yellow Pipe around the CP.
From a playability standpoint the two 4 ways and three buttons need to be one or two inches higher on the panel. Otherwise the heel of your hand will be resting on the Player 2 buttons. Likewise, your three buttons for the trackball are unplayable because your left hand would have to rest on top of the Player 2 joystick and the Player 3 buttons. I'm not sure where to move them. Your controls as printed seem to be too big for this size layout. I have a 38" wide panel and my controls aren't nearly as close together as yours

Everything I'm telling you is from my "artistic" background as a photographer and my personal experience building a control panel with playability issues (i.e. too much s**t on there).
Here are pics of an art update on your panel and my 38" panel to compare layouts.