I've started acquiring Heroscape terrain for just that purpose (well and also for rpgs). Apparently the standard that most people use is that two heroscape "levels" is one BT level.
We have a ball playing CBT on the HS terrian, I went so far as to drill some hexes and add trees for the light and heavy woods for a better aesthetic. Some players use the different colored hexes for the different terrain but I like seeing the interference. I would also suggest using a hexed map for the base level, unless you intend to purchase a LOT of hexes.