Any tips on making map Piece icons?

[HwitVlf]

I'm working on some cliff Pieces and was trying to figure the best way to make icons- meaning the little tile bmps that show up in the editor. ‎  Does anyone have tips on how to make those icons so they are easy to comprehend when building maps? I expect Ben would be the expert but any tips would be appreciated.

I think confusing icons was the main problem with Todd's cliff set and also several of the Japanese Piece sets.