How much filtration do you have on there? Some pygmy cories wouldn't be a problem in a small school but with enough filtration you could get a properly sized school (5 or 6) for them to feel more comfortable. You could definatly get away with a school of pygmys with the right filtration.
I don't think shrimp would fare very well with those black skirts. They're quite the gluttons.
By overfiltering and keeping the tank heavily planted I can keep 6 black neons, 5 panda cories, and a pair of rams in a 10 without any water quality problems. It's been over a year and the species change from time to time but the bioload stays the same and I've had no problems with the water or lost any fish.