>>716781367
you mean the user configuration option or the image itself?
for the image itself i'd say it should varied enough so you dont spend a lot of time bruteforce matching; it also should be contrasting enough but to allow the subject to take the protagonistic role
for the user conf, i set it to sky blue, but that's merely personal choice but also very puzzle-oriented. if the puzzle were to be mostly sky blue, i'd obviously change it to something more contrasting, like a pastel green; personally ive been doing good with sky blue