This is not a bug report, just something to put in the "edge-cases to optimize when you need a break from other complex things" department.

DF's wallpaper tiling is reeeeally slow if you give it a tiny image. Which is obvious since it's probably just repeat-compositing it like you normally would but you might as well throw in a check and simple optimization for small images, shouldn't be too many extra lines of code

Love your software.