Are you allowed to put marketplace offers in ur signature like "Selling btc IM Me?"
Mmm, would that have to be the Currency Exchange for that example?
Yes, you need a thread in the corresponding section (approved thread of course)
then you can add an image in your signature space / or text which is leading to your thread or IM.
You are allowed to offer services in your signature as long as you have an approved thread in the marketplace corresponding to it. @sethburster