Side tip: The reason in some MS games the CPU launches to a very high statis is because of everything on the map such as NPCs and others. I would try and reduce the file sizes and create a better packet system.

Actually, only your viewable area + 2 tiles are needed

well i will have to agree with both matter that it will take up ram and cpu but the important fact is to find a way to make it into bigger maps . instead of using the whoel thing or the little maps for each screen that is alreay in use i suggest using a variuos size since it wound increase it to much or decrease it. In this i prospect making it so you can use the whoel map ideal but makign a map editor that allows you to edit the whole thing with the capibility of spliting it up in maps so this way a map that woud normaly use 45000 would use about 10 or 20 maps the maps then only load the one your standing on which makes it faster than loading the whole thing. and to have such a big map it would slow it down having the small maps liek now would slow it down becuase your constanly loading maps when you walk on them. doing this you only have to reload the map if your near animation or if you step on the next map then the old one dissapears and has to have it load agian when you step back upon the map. But thats just my logical thery which someone coudl prove me roung.