How many icons do I need to make for a new improvement?

[sclera]

Having a bit of trouble here, I've made an icon for my improvement and it looks fine in every instance, except on the Builders' build menu. See here:

Common sense would dictate that the game would grab the same icon for build suggestions as build menu, but apparently not. Sizes I've made for the icon are: 30, 32, 38, 45, 50, 80, 128, 256. I'm sure some of those are redundant, but I put them in in an effort to make it render properly in all instances. In vain, so far.

 

[sclera]

Figured it out! Don't include any icons smaller than 38x38; the game will use them in the build menu and stretch them out.