Yeah to set load screens well, you need to know the file names of the screens you want the area to randomly pick between. You cant just say "I want this area to load with forest looking screens," though that would be nice.
Precisely setting the loading screens on all the areas would take... a loong time and isnt really that important.
I think a lot of areas are somewhat customized as to which loading screens show, just sometimes you get one thats out of place that slipped in.
-TV