Panther Animated Icon

I've been seeing these little pixel animation icons and I thought it would be adorable to make my own. So here's one of Panther. I'll probably do one of Ash too.

Now I need some help. For hours I've been trying to upload this as my avatar. I am aware that it needs to be 50x50 and under 15kB. It is. It's even under 1kB! (I don't even know how that happened...) 702 bytes to be exact. The original was about 2kB but I sized the file down by 'saving for web' and making the color count (I don't really know what it's called) to I think 6. I don't understand why it won't work. It's supposed to be 50x50 pixels, right? Every time I try to upload it, it gives me the error message of how it has to be 50x50 and under 15kB. I'm so confused...please help D':

This is mine and mine only, no one can use this animated icon in any way. Thanks