It some times takes a few days for them to get approved. Just depends how backed up there are. But never fear, they will get approved or denied before to long. If approved they will spawn in the cockpit of your ship.
Sigh, does no-one read Sim News posts? Custom NPCs are currently not being accepted/declined due to a bug with the tool. WHen the fixed tool is ported over I can then go through and start accepting/declining submitions.
Also, from what I have been told, with the new tool the Custom NPCs won't exist until they are accepted, and so we won't have this confusion with unplaced NPCs.