Since nobody replied to my post here, I decided to try to make icons for some gamepads, specifically:
Sega Dreamcast Sega Mega Drive (6 buttons SJ-6000/MK-1653) for the 32X NEC SuperGrafx (with the turbo switches) NEC PC Engine Duo RX (similar to the PC-FX)
I adapted/ripped from existing images (the NEC ones are directly edited from the PNGs at the assets folder) so use them at your own risk.