Digital Tree

The job is simple: A christmas tree build with pictures posted by users through a login or twitter/facebook connection. The top of pictures will be 10000, however the tree must be resized each 500 or 1000 users (aprox) and when is filled, then grows for add more pictures (staring with 500 users). The tree can be zoom. We need mostly the graphic approach and tecniques to do that (through css resizing / svg or some sort of that), this procedure must be capable to work with 10000 pictures in the browser without delays.