How about alot of forest/desert/snow/underground enviroment props? Making a large outdoor enviroment setting is easy, but we don't have much props to use for them.
********Underground********
-Stalagmite
-Stalactites
********Desert********
-Tall Cactus
-Short Cactus
-Dead brush
-Tumbleweed!

-Tall Desert Trees
-Building blocks/stones to make ruins?
********Snow********
-Pine Trees (Variations of snow on branches)
-Wooden Fences (Variations of snow on wood)
-Pinecones
-Tall dead trees
-Snowman
-Snowballs
-Lamp Post (Warcraft 3 would fit nicely)
-Tree Stump
-Chopped up Wood
-Firewood (Varations of Normal; Burning; Charcoal)
-Hay
-Hay Bale
********Forest********
-More trees with bigger trunks?
-Greener grass
-Red with white spots mushrooms; Purple with white spots mushroms