Select an image you like and reformat it to 100x100pixels in jpg format.
If you need help DM me and I can tweak it for you and send you the link.
If you want to be naughty you can put in moving links (gifs) as well.
I find it is easiest to store it in the site Peter provides (tm-img) and use the links from there

If you go into your profile )top right near your name)
edit profile
drop down to avatar
click the "url to avatar" button
insert the link to the image or gif.
Hit the save at the bottom.

refresh the page.

Everyone loves a Morgan. Even me, unless it's broken again.