1. Forested mountains. Lower altitude than alpine mountains, this could also be the hills terrain. The hills in CTP1 (don't have CTP2) didn't visually interface very well with a mountain range, of any type. Forest tiles work better as a neighbor to mountain, which leads me to add that there should also be a coniferous forest tile with snowfall as an interface to polar mountains.

2. The desert mountains only interfaced well with desert and plains. The desert hills didn't stand out as an intermediate. Try making the desert hills look rockier, like maybe mesa structures or rock towers. Also consider dunes, the functional equivalent of glaciers in the desert.

3. Consider giving glaciers a thickness which partially consumes neighboring mountain tiles. Or, they could be a mountain type of themselves, glaciated mountain.

4. Palm trees for interface with desert, willows and reeds for swamp. Exploit the larger tiles with more creative variety.

5. An occasional volcano would be a nice touch. Maybe even active. In some places you can't have a civ for 1000 years without coping with this from time to time.

6. How about an "Island cluster" tile type to make coastlines look more broken and complex. Functions as shallow water.

7. Finally, don't let tile improvements swallow up the whole tile; example is the robotic mega-mines. Can't even see the mountain anymore.

I agree that CTP benifited from larger squares, but did this mean you couldn't have as many squares on screen at once, as in Civ II?

I agree most strongly that Firaxis should go out of it's way to avoid invasive tile improvement graphics. See SMAC and CTP for details...
I feel Civ II, although with it's noticably primitive graphics, had the balance just so.