[EDIT] Yes, it does work.
Looks like you have it up above?!?! With that image now stored on linux.org (URL: https://www.linux.org/attachments/rqfjpo4-gif.3860/) you should be able to use that as the URL in your Signature settings. This worked for me, as you saw with the Garfield cartoon. You may have to re-enter the whole signature from scratch though... not sure about that.Close but no cigar, I'll keep working on it.