I don't think we have anything specifically for before and after shots (although that sounds like a lot of fun). We do have a forum for photos of peoples' gardens:
http://garden.org/forums/view/...
We also have a newish feature called "Image Sets" that lets you look at peoples' gardens along with names of all the plants in each garden. You can see that by clicking on "Webapps" up top, then click on Image Sets.
