Pearl Danios (Danio albolineatus) are wonderful, but just to clarify, I was talking about Celestichthys margaritifer (google helps; species names are the only way to know we're talking about the same fish, sorry to ramble)
if you want to try something interesting go get a feeder minnow and then feed it top quality foods and watch how what most people just plunk in for food develops into a very interesting fish.
I have done this a few times with various minnows and was very surprized at the color of the fish as they grew.
Other than that some nice organic planting soil and an african violet.
i would say cherry shrimp, but only if you have another tank to put the fry in, since they breed like crazy. but they are a nice contrast to a heavily planted nano tank