As title say s why ain't it showing in my threads
You have two avatars: the one listed in your posts and the one seen when viewing your user profile. Ya put your avatar only as the profile one.
If you put your signature in as the "signature picture" when editing your signature, don't bother with that feature. It seems broken. Link to the image you want in your signature in the "edit signature" text box and save it. I recommend usin' photobucket or somethin' similar.