Yes just make sub directories for your free sites. 20 to 30 pics should get your listed at 99% of the places. I have no set rules for movie sites, guess I should make up some rules for that, lol, but I would say 10 movies would work for my link list.
Don't forget to add some AVS doorways into your free sites, another nice source of traffic.
This is how I do my sites,
I take 30 pics and build two TGP galleries with them and then using the same TGP layout I add a main page and a warning page and I have a free site. Then I add a few AVS doorways to that as well. So pulling from the same 30 pics I get 2 TGP doorways, my Free Site doorways, and a few AVS doorways. By the time you count all the doorways I end up with close to 1600 doorways all going to the same 30 pics.