FlickerKaramba Interestingness is another simple widget for displaying flickr photos. This one doesn't use tags, it grabs photos from "interestingness" so you get all kinds of good stuff.
The widgets don't have borders (although it looks like they do in the screens), you can set width, height, anchor point, ect from the right click config menu.
If you run multiple instances of the widget and they share the same image dir (they all will by default) they won't display the same thing twice, ect.
I threw it together quickly, but one word of caution don't try to mix your own photos in with the flickr ones, they could be deleted upon a refresh.
Oh, and you need to get a flickr api key to use it, freely avaliable at their website.