Thank you for all your responses!

quasarchangel - It is an indoor level (my outdoor levels use terrain), so I am using blocks, and I have the TGA barely above the ground.

The model method would work, but that presents another minor issue: the TGA is animated, to look like raindrops are falling on the texture. There are 8 frames of this. Is there a way to animate the texture of a model (8 frames worth)? If there is, then that might be the best way to go.