Campaign Map Editing and Ground Textures at Higher Altitudes

I've been playing around with editing the campaign map and have decided that larger variations in altitude are a lot more interesting to look at, not to mention the terrain on the battle maps becomes quite cool. My problem, however, is that at the higher altitudes I need for this effect, the normal ground textures are gone, leaving only an awful, bland white color.

I've searched about and am not yet sure what I can do about this. The question I want to ask, I suppose, is does anyone know how to edit what textures do at higher altitudes; or under what circumstances do they undergo change or simply end? It seems to me that, at a certain height, any given ground texture will simply end to create a sort of "mountain-top" effect. If there was a way to change the parameter(s) for this I'd like to know.

Also, I am aware that sometimes (at least in other games) lack or problems with video memory can lead to a bland white replacing textures. In this case though, at low altitudes the textures are fine.

Anyhow, I've found a bunch of files regarding ground types and textures, but they're all rather cryptic. Anyone have some understanding of them that they'd like to share? I'm pretty lost.