pictus would be great, fun to look at and very very active, should stir up the substrate to premote better overall oxygen levels in your tank. One thing about the pictus that you should be caregful about the is not to catch them in nets they have an ability to stick out bones from there sides making them stick in nets which eventually forces you to basicly just cut the net, so they should be caught in a platic cup. As for the neons angels and serpaes, it really all depends, angels can eat neons and serpaes can bug angels, but every fish is differnt if they all seem to be getting along i would say dont worry about it, there are always exceptions. I do personally believe that you should add more to your serpae school so they tend to chase each other instead of your angels. And as for the neons i would say just moniter the situation and be careful, if you see the angels start to get aggresive around the neons remove the neons or angels asap, because the results will not be pleasing. But like i said all fish are different, you may never have a problem with those fish at all.
-Jay