Here is a quick example of what you can do with a little bit of styrofoam and paint.
Take a few styrofoam set pieces. Arrange them to look like something cool.
The pieces are modular so they can be moved around for this shot and can be stored for the next shot.
I like this shot. When you arrange your pieces how you want them, take a ton of photos. Not all of the background needs to be filled in. It is always nice to have it all in place, but if there are some places you have no styrofoam piece then you can fill it in in photoshop later.
You can fill in the blank areas with green if you wish. Then you can fill the empty areas with painted in filler.
It is not perfect, but it will do for this shot. Now you can adjust the lighting digitally as well if your lighting in real life was not done to your liking.
In my shot, a torch is burning. Then a water arrow is shot, and then it goes dark.
As always, the more pieces that you can create in real life the better it will look. The lighting will look better if done in real life as well. But tons of stuff can be done if you have some photoshop skills. So, for a three second shot, we accomplished it with a few chunks of styrofoam, and a few minutes in photoshop.
Go ahead, make a mess, have some fun, make some fake sets,