I think I've narrowed it down to 2 potential maps to use as a base to start from. They have all the territories I need: desert, forest, snowy mountain, and plains area.

The first the southern tip of south africa:
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vs.

Northwest Mongolia:
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Each of these terrains consists of 25 sectors (25 3d models and 25 textures) that tile together seamlessly and are low poly enough to use on mobile. I'm going to repaint the textures of whichever map I decide to use with ground textures and populate it with 3d buildings/plants/trees/etc.