Well the system is made so I could easily create maps, not for reserving memory.
Each tile is 24x24, probably means it'll take a 32x32 memory of VRAM if what you guys say is true.
Since every map reloads the tilesheet I don't think it will overload the system too much, even of your computer is a tad old.
Another question though, guys: is it possible to encrypt archives with a password only the game has an access to, in order to store my files? Since almost nothing is reserved as a resource, I'd like to protect my files; I didn't find any password function within the ZIP object. So, what method could I use?