The user avatar supports .PNG and .GIF as seen if you try to upload an unsupported image type:
Sorry, the file you are trying to upload is not authorized (authorized extension: jpg, jpeg, png, gif, java).
but despite the fact that both of the mentioned support transparency, if uploaded they get a black background. Keep in mind that both formats also support partial transparency.
It would be nice to support transparency because the background colour behind each of the places where the avatar is used. I have changed the background of my avatar to match the background behind it on the profile page, but that does not match that in the navigation bar nor that in the user card.
I don’t know how difficult it would be to fix this, but it would be nice.
This isn’t something overly difficult to fix, heck I made a stylesheet that runs on a chrome plugin called stylebot and I was able to add transparent backgrounds to it just fine, if you want to see it click here.
Screenshot as proof:
https://forums.spongepowered.org/uploads/default/2521/57692293df998770.png
I have a transparent profile picture even before I used Stylebot. Are you sure you rendered it right. (Not Paint…)
Well, my avatar is partially transparent. I don’t know what’s the issue with your avatar. It may just be that your immage uses an unsupported transparency color and isn’t displayed correctly due to that.
It’s inconsistent, look here the one in my post has a black background, the one on my user card has none:
All one screenshot, and I refreshed the page multiple times before taking it.
Well, transperency works here now 
Do you not see what I do, my avatar on my card works but not the one next to my posts.
Well, works for me. Didn’t earlier.
Your saying the 45x45 image below is not transparent for you? Have you reuploaded the image since you first posted? It transparent to me in Chrome, IE, FireFox and Safari on Windows 7.
https://forums.spongepowered.org/user_avatar/forums.spongepowered.org/tebbenjo/45/2557.png
https://forums.spongepowered.org/user_avatar/forums.spongepowered.org/tebbenjo/120/2562.png
Yah, and their different, the small one does not update, the larger one does. It may be a chrome cash thing, let me check in firefox.
Nope. I bet that the server takes some time to convert the 120px to 45px so that’s where the lag is from, and that’s why I couldn’t see the transparency immediately after I updated it.
