no photo ads, single photo ads, multi photo ads, paid options to ad to ads.
small donkey - did you mean no photo ads in the beginning of that post? I'm confused by it as the post goes on to detail examples of allowing photos in ads. Maybe I'm missing the point?
Here's an example of a classified site I run using e-classifieds.net's solution. It's very detailed and well thought out, as you'd expect from a paid-for solution. If something seems to be missing there, it's because it's an option in a higher-end version - mine is mid-pack in their range of options.
I'd suggest taking the major cues from something like this and adding the nicer items folks want and detail here.
http://www.freejeeplistings.comThere is definitely more than one way to skin this cat (skin this app???), so my vote is to take the main features used by systems with time and money invested in R&D and add on niceties and thoughtful touches from there.