The reason this came to mind to post about was that I bumped into the BBC's Viewfinder blog, and the Your Pictures On A Theme page.
Anyway, on to Cooliris (used to be called PicLens).
Cooliris Browser add-onIf you don't have it, you can download it for Windows and Firefox here. Go here for other browsers
The add-on allows you to click an icon that appears on images on any site supporting it (like flickr or google's image search). You then get a wall showing all the images (the wall just goes on and on, as long as there are more images to fill it).
You can also embed the wall when you have a supported feed type for it, like mine below. This is from (and all of) my mono gallery:
Feed source / locationIf you're interested the feed for the wall above is at http://www.highton-ridley.co.uk/monochrome/photos.rss
As with all free tools like this, you have to put up with adverts and various attempts to persuasively hijack you to other places. But other than that, enjoy!