probably far to late for this to be added to CW2 - but something to consider for CW3 I hope ?
just having 7 blocks to play with doesn't give the map maker much choice to be able to create real works of art like in CW1
custom graphic 'overlays' - I'll do my best to try and emplane what I mean - 2 ( or more ) custom pictures for your map - one makes the background image and the other only appears where there is earth left - so digging the earth away changes the picture for that space - earth types could me shown by texture overlay of the custom image
The terrain background can already be changed as far as i know.
You can use transparency in the image used for the tiles to let some of the background show through your terrain.
Oh god! That means I CAN do my next project! Never even thought of that...
Look at the map I made (Fragile) That was a transparent tile test map.