I would love to see the ability to define (multiple) watermark images and the option to apply them to uploaded photos automatically or manually.

I would also love to see a basic and simple shopping cart plugin that allows you to sell your photos/images.

eh, I don't know about that, it seems like something like that would make Zenphoto turn into ComplicatedAsAllGetoutphoto. I would look around at other solutions just because I don't think that is the sort of thing that Trisweb would want in Zenphoto. But, if it is, I am sure it will be exactly what you want.

Then again, the watermark wouldn't really be that hard just not that useful to most of the users who, use this for personal sites.

I do not need any shopping cart. I would only use this for a personal page. BUT - I would like to have a watermark added. Just because I would like to put my mark on my pictures. Even if it is a personal page, I still hold the copyright on my pictures.

Ive done a couple sites for people using zenphoto and both of them needed watermarks, that would be a great feature to have.