I don't know why it's not showing. It meets the avatar requirements (max 100x100 pixels and 40kb, jpg or png). Yours is 84 x 100, 6 kb and is a jpg.
You might want to post the problem in the Forum Issues section. It's been my experience that they fix stuff pretty quickly during weekdays. You might be waiting till Monday for a fix, but I'd bet you half a peach that they'll get it soon after.
There's no direct route to it from the GalCiv3 forums, but you can get there from the Stardock Forums. https://forums.stardock.com/forum/503
