What size tank? You could probably put in a couple of snails, but keep in mind that shrimp love to groom their tankmates so something like a Mystery snail might get annoyed after a while. I recently set up a tank with only shrimp and I love it. They are so much more active with no predators to worry about.
I have a 10 gal now with nothing but cherry shrimp Im hopeing to build a colony while i work on a larger tank prob a 55 gal i thought i would ask before i bought tx