It is possible in Family Tree Builder to make different catagories of photos and documents, but on the web site all photos will be stored in the specifik catagory and in the Family Photos catagory. This means that photos are allways "stored" twice if you are going split you photos into different catagories.
In you do not have the premium plus membership this means that you total number of stored photos are only half the number mentioned on the upgrade site for the Premium membership.