Couldn't you create a second image gallery and just call it classifieds? Image gallery has image and description, and people have to be logged in to submit, so they could just upload an image of their thing to sell and put all the proper info in the description. If they don't have an image, they could upload no picture, or maybe a picture of nothing (e.g.- 1x1 pixels) or even their just avatar. An added advantage is that there would be a discussion thread attached to the item so it could be discussed and questions and answers could be posted, etc.
What say?
