Right now only people who are logged in will be able to upload photos. I think we will probably keep it this way, although we might add in the ability for anyone to link to an image (with the forum owner's permission, of course). As for the amount of space, it's currently unlimited, and chances are that we'll keep it that way for a while.
We won't be able to upgrade the Network54 forums with these features - we wrote Visigroups from the ground up and it's entirely separate from Network54. However, we do plan to have an importer from Network54 to Visigroups, so you'll be able to move all of your old posts if you choose to, or keep them running on Network54.