Bidirectional Sync of iPhone/iDevice Photos and Albums to Third Party Clouds
Try Unbound app. It uses dropbox to allow you to organize your photos on your ipad. So you can move, delete and rename photos on your iPad and the changes are synced back to your dropbox.

I tried it and liked it, but I don't use it, because all the managing functions (move, delete, rename) only work, when you are online.