First of all, let me suggest that you have at your disposal this great document created by NPC99 dealing with basic concepts of world mapping (source thread).
Quote about scales:
How do you scale your map? There are a lot of factors to consider, including:
Shape - I recommend a square map to match Main_map’s outer_mesh border and because I had trouble rendering Vista textures on non-square maps.
Vertices - @gkx recommends between one and two vertices per metre to optimise performance (i.e. 53x53 or 106x106 single node dimensions for Calradia). While @cuce created Calradia using 256x256 to increase geometry for artistic terrain (i.e. 256/53 = 4.83 vertices per metre). Take your pick.
Nodes - the hard-coded maximum is 16x16 nodes.
Size - technically, nodes can be any length, but may stretch the same number of mesh polys into large triangles too crude to sculpt.
Is there an alternative to larger scale maps?
@John_M said: I wonder how practical scaling down characters, floral, and settlements would be.
@cuce said: really practical, it's just some number on some .cs and towns and entities and flora are just regular entities on the editor, you can scale them down as you wish.
Problems might come up with generated entities like catapults and trebuchets whose prefabs will need to be rescaled as well. Another problem might be particle effects.