I assume its fully cycled for your bioload.
With that stocking, you have virtually no limits in terms of fish to add, excluding some African cichlids.
I like a big shoal of one type of fish or another. There are plenty of shoaling small species of fish that would look fantastic in your tank.
Options:
Trigonostigma espei (about 1.25-1.5 inches full grown), T. hengeli (slightly bigger) T. heteromorpha (Known more widely as harlequin rasbora grow to about 2 inches) all are VERY peaceful and great dither fish.
Five banded barbs (similar in look to tiger barbs, but far more docile, nearly skittish) - grow to about 2 - 2.5 inches.
Tetras:
neons (2 inches) or cardinals (up to 3 inches) - red and blue colored. Brilliant colors.
bloodfin or rummynose - tight shoalers each about 2 inches.
black or red phantom tetra (2+ inches)
black or white skirt tetras (2+ inches)
Corydoras:
dwarf: panda (1.5 inches), C. hastatus (1.25 - 1.5 inches), C. habrosus (1 - 1.25 inches) C. pygmaeus (1 inch)
regular: trilineatus, julli, peppered, sterbai, etc. (2-3 inches)
jumbo: Not truly a corydora, but similar: emerald (Brochis splendens) (4 inches)
Plecos:
small varieties like bristlenose or clown, pitbull.
(Gotta be careful because some are tankbusters)
Apistogramma/Rams:
Bolivian Rams or various apistogramma - as single individuals would probably work best.
Keyhold cichlid (5 inches) would work with the larger fish)
Gourami:
honey gourami, or dwarf gourami