The Cory I would add last they're very sensitive on new set ups.
For Crayfish or Shrimp there's a TON options here now. In a community set up its much easier to house a dwarf cray (like a cpo) then it would be with shrimp simply because of your filter intake. Now while I loveeeeee dwarf cray's (see my aquarium log "CPO tank") some of them you really gotta evaluate carefully - The CPOs for example are wonderful to keep in planted tanks and they stay fairly small - Some others not so much and I'd not want you to wake up one AM and your plants have vanished.
I also put together a shrimp guide here http://www.tropicalfishkeeping.com/f...keeping-37012/
if you're really interested.
Please let me know if I can be of more help about cray's & shrimp they're real awesome