Making the eggs too small like 16x16 to 31x31 is frustrating for users to click on, 32x32 is a perfect size.
Making them too big also is frustrating as it makes signatures too long in some cases, and there are forum boards out there that have guidelines, so stuff like 65x65 is pushing it.
Obviously if you have a circle egg it would be weird, so you can kind of be flexible.
Not too big, or not too small.
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