You need BO1 DLC inorder to see the grass effect. If you don't have DLC the grass will appear as big black blocks.
Trench Defense from the Dawnville Map Pack in World at War returns in Black Ops 1. Survive in a small trench line. Perks are earned via killstreaks. Upgrade your gun with headshots. Survive 20 rounds to unlock the game ending round or survive as long as you can/want. All of the BO1 guns you know and love, plus some custom guns. Those that played the map in WaW enjoyed it as a small challenge map. Ported it forward to BO1 to give more people a chance to play it.
One known issue is some zombies will just stand at their spawn point. I tried for days to fix this but never found the reason it was happening. You can shoot them at their spawn, or wait for them to respawn.