Uhm, I think we're mixing things up.
In the case of posting content:
You can post anything you made (like a new horn) on the forum, or give a link to it.
But other people's work, other people's horns or lights or whatever, are off limits, unless you have permission.
But with a signature image, it's no big deal, if Capt.Bluebeard makes you a sig, then you can just put it in your signature box, that's what it's there for, by making it for you (if he does), he allready will agree that you post it out in the open.
Fred.