The more you help and submit requests, the more you can rank up your post count.
The avatar layout restrictions are:
Let's try to keep signature images under 100 or 200 MB so pages won't take forever to load. (I'm not sure what's okay here.)Maximum dimensions; width: 100 pixels, height: 100 pixels, file size: 9.00 KiB.
Let us know what programs and tools you like to use, or tips in general.
I've been using MS Paint to scale images to the right pixel dimensions in bitmaps then exporting to jpeg to reduce the file size.
And if it is alright, here's a link to the late Desbreko's prolific screenshot library to help people find some source images to edit.