Well, you could make the Classified Forum for posting ad's a photo gallery forum, then they could upload X amount of photos and use the standard post area to describe the products.
Another alternative would be to enable attachments in that forum, then set the inline photo option to X amount of kb's, so anything under the limit will show "in line" (vs users having to click to see the photo).
Semi curious how photopost does their classifieds though; unfortunately I don't have funding available to purchase said script to take a gander at how it works lol.
