the only time formatting matters is when you have a pregnant (other category) file then it's preg(other category) rather then pregnant(other category) or preg (other category) I don't think preg_category works. but I think one of my girls was done like that.
other wise you can have 'anal christmas', or what ever you want, as long as 'anal' is first, it doesn't matter what is after it.
there is no limit on the number of pictures, just make sure they are all jpg or have .jpg at the end of the title. else they won't get picked up by the game