...create launching images that would display the control scheme for every game (but that's way more effort than I really feel like going through).
That's exactly what I did for Arcade titles (with a copy of PhotoShop and a PC), but it's a big time investment. I did about ten/fifteen "major" games and then figured I'd get to the rest eventually.
I'm able to "re-use" some work for games that have the same controls. (e.g. Pac-Man and Ms.Pac-Man both use the "no buttons required" image) I also tried to make the button naming generic so that I can re-use images. If the buttons for "shoot" and "jump" are in the same place then I re-use the image. So far I've done early arcade titles which simpler control schemes.