If you want some more colour in schooling fish congo tetra's especially the males colour up beautifully also rainbow fish. I have both in my 180g tank and they actually school together. As mentioned above the larger the school the better it looks, especially in a planted tank. JMO
As for feature fish that is a very personal thing depends on what you like personality/ colour etc. But with the schooling fish in your tank you will want to avoid fish that like to eat smaller fish. I once put a school of 20 neon tetras in one of my tanks not realising that my 14" BKG would make a meal of the during the night. Only took him 3 days to eat the lot.