I love this set, c is my favorite language! I get that the mod text colors are supposed to match a vim colorscheme and while that is a neat idea I don't think it would look good on a keyboard in my opinion I would love if there was a monochrome base or mod kit.
Maybe there is some reason behind it, but I don't understand why the null is in a red box like that and not all caps.
Also huge missed opportunity for a segmentation fault keycap.
Great work though, even if you don't end up making any changes I will definitely still buy it!