After posting in another thread
[earlier today] about a related topic, I noticed a part of "Signature restrictions" is still outdated...
The description part for the "Avatars" sections needs a little update as well...
It must be no more than 120px wide, 80px tall, and 100 KiB in size. It must be a PNG, GIF, or JPEG image. It must be safe for work.
non-animated PNG