Right now the only valid resolutions are
8x8, 16x16, 20x20, 22x22, 24x24, 28x28, 32x32, 36x36, 42x42, 48x48, 64x64, 72x72, 96x96, 128x128, 160x160, 192x192, 256x256, 384x384, 480x480, 512x512
It would be nice to also support 1024 and maybe 2048, It might not bring much difference, but if somewhere in the user's end the appimage has to appear big it can be a bit pixelated, also gives the options to have it on bigger resolution for people that want to instead of being limited to just 512