A good idea for your Necromunda battlefield is to include a River of Slime running oozing it's way across. Not only can this look cool, but it gives you the oppertunity to use my new house rules...

A river of slime oozes it's way across your battlefield. Although it is possible to wade through it, such rivers are often known to give off dangerous vapours, and hideous creatures often lurk in their dark depths...

MOVEMENT

Wading through the river requires a great deal of effort. Models attempting to move through the slime move at half their normal movement rate.

HAZARDS OF THE SLIME

At the start of each players turn roll a D6. On the roll of a 6 the stream begins to bubble... Roll another D6 and check the table below.

1. The stream gives off toxic vapours. 
   Any models within 5" of the river are affected
   as if they within a cloud of gas from a hallucinogen grenade.

2. The river begins to bubble and spit. Any model within 3" takes
   a S3 hit.

3. Thick gas from the river blocks the line of sight.

4. A creature emerges from the slime. The closest model to the river
   takes D6 S4 hits.

5. The stream gives off choking vapours. 
   No model within 5" of the stream may move for that turn.

6. The slime begins to burn through the skin of anyone in the river.
   All models in the stream are DEAD. Not out of action, DEAD,
   as in result 11-16 on the results table.