I have some suggestions for the borders:
- It'd be really cool if the custom borders could be scaled to aspect ratio to fill most of the screen.
- It'd also be neat if the borders could create a pseudo-3D effect in 3D mode, like some of the 3D Classics and 3DS Virtual Console. What I'm talking about is the the image inside the border would be "pushed in" when 3D is turned on.
- And of course, SGB border support. Bonus points if the border could be "probed" so you can play in GBC mode with the border, like in Pokémon Stadium 2's Game Boy Tower and the BGB PC emulator.