How many gallons is that? I like arabian dottybacks in nanos. Super bright with nice lighting! 6 line wrasse is also a good choice, and does a good job keeping pests at bay. Other than that, maybe one ornamental shrimp. You could also do the pistol shrimp + goby combo, that's really popular in nano reefs. Your firefish will be mid-top water and the goby and shrimp are bottom. All sorts of gobies and blennies to choose from really.
But I would probably stick with 1 shrimp and 2-3 fish tops (depending on what fish you get and how many gallons your tank is, I can't tell). I have a true percular pair and a six line wrasse in my 29 gallon now, along with a coral banded shrimp.