I need to make the terrain on my map shimmer. I tried adding a layer of water but due to the size of the map this was not possible. I have seen some maps with sprite of some kind floating a little ways from the ground as some sort of mist. Is there a tutorial for that or does anyone have other suggestions?

Shimmer? In what way? Can you be more specific. Do you mean heat wave shimmer one might see on hot asphalt or desert sand?

I am attempting to make a terrain that looks like a plasma. Fluid, but not specifically liquid. A heat wave is about what I was thinking. Thanks.

You might be best off with modeled terrain.

Look in the stock dagobah assets to find the ground mist prop, otherwise maybe use hex editing to make a model glow and use it for the ground, like what I did for the lava on my Mustafar map.
To add a light bloom glow to a texture by hex editing, simply change the 6th (or 5th?) place from "ATRB" to 02 on the hex side for the texture you wish to alter.