I think that this is a neat suggestion, yet I think that people could just post it under the "Other Services" subforum.
I vote a yes to this though, or some other sort of Services thread (Text/Userbar/Signature/Avatar Services, if there isn't some sort of forum for this already.)
Well, you can't really remove your own thread, but the user services sub-forum is under the Runescape Black Market, though, therefore should be used for Runescape trades only..