nanosweeper mode needs to change colors when cleared. It's really hard to tell which square is clear and which is available

Agreed. However, to be honest, Nonosweeper mode is just a fun add-on I put in after creating the separate Nonosweeper software (http://www.nonosweeper.com), so I didn't put too much thought in. It's far easier to play Nonosweeper in that software because it doesn't allow so much customization as CryptoPics. The only thing it can't do is load image puzzles.