Hello Whisper (name edited for privacy),
It's always sad to that a forum will close the doors. Which one it was ?
About Avatar and signature for non profit, there is no problem, I even
give the permission one year ago to a whole community "avatar and
sigies" if I remember well, to use my artworks for make non-profit
avatar and signatures.
Hey I've been admiring your art on a forum that is shutting down due to inactivity. Usually I would read the FAQs, however, I would like to request your permission personally to see if it is indeed all right to use your art in avatars and signatures (Non-profit). With leaving a copyright back to you.
Hope to hear from you soon.