I got it to launch and run, checked the help file for how to do things.
I got some results, but it is obvious that the quantity and variety of your source images are very important to getting attractive results (my couple-dozen set of pics made a pretty homely mosaic). I don't have time to explore right now, but it is an interesting app!
A good start -- good luck with this app!
Pebbles
graphical tool, to create a mosaic image from a base image
Version: 1.0 Public Beta