Fade between two images in a particle effect

Hello Everyone,

Right now I have a particle that falls in the background of our game. Currently the the particle effect has a sprite sheet attached to it with two pictures, one of a "1" and one of a "0". We are trying to go for a computer theme. Right now if we just have those two images unity will just flash back and forth between them. I'm aware that I can control the speed, but it still looks weird going from one directly to another image. My question is how could I get these two images to fade back and forth between each other. The best solution I have is to create a bunch of images between the fading in photoshop and make a really big sprite sheet. However, this does not feel right to me. Thanks again for your time and help.

-Marc