Or: the people that really think they have something worth selling (i.e. not spam) will take pictures and pay to post a few of them. This could actually make it easier for buyers to spot posts from serious sellers. The number of pictures may indicate the seller's confidence in the product. Of course, there's still the potential for spammers willing to pay to post pictures, but at a dollar each I don't think the margins would be anywhere near, say, email spam which costs virtually nothing.

But if it's targeted at people who are causally selling their crap, not products, then you want lots of photos to be sure of the kind of crap you're buying. The seller might just want to unload it.

It does seem a little silly, though that could be said for most things that haven't been tried before. Couldn't you just combine a bunch of pictures into one huge image? Or if size is limited, you could just have an image that has a URL of an external picture gallery. I applaud thinking of a revenue model early on but I would think there's a better way..

No URLs. No HTML. Pretty much if you have to pay to put an image, you can't do any links or external content, and the email interaction is fairly controlled, then putting up spam will just be annoying.

Also, if they want to do one giant image then fine, it'll just load like crap.