Crappies are one of my favorite fly rod fish too! In the places I fish they don't usually get very big, and a 10" fish is a brute. On a 3 or 4 wt they're great!
I posted some flies awhile back & a few weeks ago of some I tied that I would use for them & other panfish. I have a couple of boxes full of buggers too that Ill use. I'm also a big fan of olive buggers, but pink & white also works well on Crappies.
Spinner Flies, size 4 hooks. Would use these with my 6 wt.
Simple Streamers, size 6, no added weight.