What kind of planting and hardscape do you have in mind? What kind of water parameters do you think you'll have? Will you use RO/DO and a mineralizing agent or just treated tap? Settling on that stuff first would make it easier to give suggestions. Might even determine what you can or cant keep.
Since you already have CPDs, it's definitely a good idea to add more. I'd stick to odd numbers for 'schools' - like 23, 25. They're impressive in large groups.
What kind of Pygmy Cory? Actual Pygmies or C. habrosus - the tiny ones that often hang out mid-column? Either way, I'd get a decent group of them, as well. If it were C. habrosus, I'd say about the same number as the CPDs. If the Pygmies you have are just as small, then definitely get a bunch of them.
Then I'd add a group of super-tiny Rasboras of some sort. Maybe Boraras brigittae or one of the other types that school a little better. I kept 55 of them in a 20gal tank and it was the first time I'd ever seen B. brigittae exhibit more school-like behavior. Have always kept them in small tanks and in groups of 20-25 and never saw much of it. Bet they would really shine in a group of 100 or so.
One of the White Cloud Minnow varieties would also stand out in a tank like that.
They're all basic fish, sure, but they look terrific in large numbers.
Would probably avoid Gourami because they don't tend to be too impressive-looking (in my opinion).
If it were me, I'd put very little emphasis on shrimp because they're not going to be a focus in the tank, unfortunately. They're going to get eaten and picked off no matter what you do - even with tiny fish and plenty of hidey holes. A bunch will survive but they may not thrive. That's why I'd probably go for something larger - Amanos, maybe.
A tank like that, depending upon hardscape, would look really cool with wild-type Neo shrimp. Various browns and splotchy, wild-looking critters.
So I'm planning on stocking my 63 gallon with nano fish and rcs. It's a moderately to heavily planted low tech setup. What are some stocking ideas? I already have 4 Celestial pearl danios and a few pygmy corys so I'd like to get maybe a school of 20 of each. Also thinking of adding pygmy/sparkling gouramis. I know they can eat shrimp but I think the tank is big enough and there are enough hiding spots. Thoughts?