You could add a whole lot (in terms of variety)...
If you like your corys, you could consider getting 2-3 more of those. While 3 is the minimum number for a "school," the more you have, the more active they are.
You might want to consider adding one, slightly larger "centerpiece" fish. A dwarf gourami would serve this purpose nicely. (The most popular colors of dwarf gouramis are the powder blue, and the "sunset" with is mostly a reddish color). A lone betta would also
likely work (though bettas are quite individual in their personalities, and some take to a community setting better than others. Femals almost always do fine; males usually are okay too.) I suggested these two options (gourami or betta) because both tend to hover near the water's surface, which is right now an area of your tank where you don't really have anything.
As for your "mid-tank," presuming you didn't want to add more cherry barbs, you could stay within the barb family and add some gold barbs. A small school of any of the smaller tetras (neons, cardinals) would work. Adding a few livebearers (platys, mollies, swordtails) would work as well.
Those are just a few ideas to get you started. Good luck, and please keep us posted.