What's the specific considerations?
thanks

Mix of technical requirements and historical reasons.
Before custom maps MDT used the base maps from the game which where either 15 tiles for most maps or 150 tiles for super detailed modern maps like mechagon. The game has certain requirements for both custom textures and game-supplied textures for example that dimensions always have to be powers of 2 (32x32 and 64x512 are allowed, but 40x40 is not, for example).
Custom MDT maps are sliced up and made to be used with the 150 tiles format.
A new format for fewer and bigger slices could probably be implemented.

All custom map files are also available in discord as both full size png and photoshop files.