I've now finished wiring everything up and the screen, buttons and sound all work, so what's next?

1. The aperture for the screen is slightly too large, exposing a little too much of the non-displaying part of the screen at the bottom. A small adjustment to the case front will fix this.
2. It's too easy to unintentionally press a diagonal on the dpad. I think that this is because it is a little too small and moves around too much in its hole. Hopefully making it slightly bigger should fix this.
3. Complete the case front and design a back for it.
4. Re-print the external parts in their final colours. 
5. Programming. Lots of Programming.