That;s a sweet looking tank!
I'm partial to hatchetfish, maybe 10-12, they would only occupy the very top of the tank, some corydoras of course, again 10-12. for the very bottom levels.
rams are great but they will probably eat your shrimp...
but so will anything that can fit them in their mouth,
a trio of pearl gouramis would look really good in there- rainbow fish would be great too but they are so active I think they would distract from the peacefulness of your tank