This is just rough (very rough) !
But a graphic like this designed per emulator, designed to match your resolution that pops up for say 5 seconds before ROM loads.
Actually another idea that I had (and never started) was a nice print graphic, like a flyer, or old school instruction booklet that was included with your NES, SNES cartridges that had a write up per emulator. It's a lot to remember when you have multiple emulators.
When I did my last install I created a text document to record the changes I made, but with my NES emulator for example I can't remember if like an idiot I selected Player 2 start as select, which is foolish, because 2 players will play.
Anyway sorry to ramble !