It works the same as posting screen-shots.
In your Profile, under "Signature" you type: left bracket img right bracket URL left bracket right slash img right bracket.
...had to type that in 'cos it doesn't display correctly otherwise...

.....!
(position it where you want it to appear).
....So upload the pic to Simviation first, and type the pic in place of the URL...
Exactly the same as you do to upload/download a pic...

...!
The upload will be:
http://www.simviation.com/yabbupload.htmland the download to your profile will be in the URL place:
http://simviation.com/yabbuploads/yourpic.jpgCheers...
Paul.
(England).