The BFAQ lists (http://www.americangirlscouts.org/agswiki/Graphics%2C_Characters%2C_Text_%26_Rooms#Scrolling_room_image_size_limits) the max height of a scrolling room as 1,400 pixels for 320x200 resolution, or 2,800 pixels for 640x400 resolution. If this was once the maximum, it is no longer the case. I was able to do a 4096x4096 background at 320x200 resolution.
Does anyone know what the actual maximum is now, if any?
According to CJ's response in this thread (http://www.adventuregamestudio.co.uk/yabb/index.php?topic=37530.msg493394#msg493394) there is no longer any limit to room dimensions, but the pathfinder doesn't scale well to excessively large rooms.
I have updated that BFAQ entry with this information. Thanks!