A less complicated suggestion, perhaps:
Somebody (AGA
) providing a system to host these personalised trophies, along with a default (or no image at all?) in case the competition starter didn't make any (no need to force making of trophies, although this method might encourage laziness to NOT make trophies), and when someone wins, it shows up on some section of their profile page (not under their avatar).
IF that person should so desire, they can copy the code or links of those images into their own signature.
Although honestly, simply having a space somewhere just to host all the trophies if that competition had any wouldn't be bad either.
Somebody (AGA

IF that person should so desire, they can copy the code or links of those images into their own signature.
Although honestly, simply having a space somewhere just to host all the trophies if that competition had any wouldn't be bad either.