I played around with some of these tools and found them to be fun and creative. My own photos that I downloaded weren't appearing yet in flickr and I had wanted to create a mosaic, but maybe later.

The steps here were to copy the html/edit html above/then preview - pretty easy. I see it's not displaying quite right because of the size of the letters, but didn't want to mess up the html and it wasn't obvious to me where the size was in the code