Have you thought about including Snow Line mod in OpenGFX+ Landscape?
Also, I made a suggestion in chat awhile back of including something similar to Grassy Knoll
(replace player-owned land w/ brown tiles & sign with grass sprites), and have an option for all the sprites to be surrounded by 2cc-colored fence. Current if I have GK and OGFX+L loaded, I lose the signs but I'm back to brown ground sprites.
I just thought about the SnowLineMod being included here might be a good idea. So: thought yes. Done anything in that respect: no(t yet); it would require a re-write as SnowLineMod is written in NFO and OpenGFX+ Landscape in NML, so a simple copy&paste of my previous grf fails here.
Also the idea with the CC-fenced area as bought company area is still something I fancy (though it can't quite replace the bought area sprite, you'd have to build the "fenced area object" instead is still something I plan to consider. But it's a lot of work to get that into the game as I'll have to query the ground tile and consider every slope possible for every ground tile variation (climates) possible (or I didn't yet see an easier road).
Another idea is to allow a switch to select the ground tiles used independent of the actual climate - and to include also temperate - snow transition tiles for alternative use in the arctic climate.
I'm quite open to collaboration on this (or other) sets, I don't have to be the single code author