Daelkyr hideouts, corrupted (or exalted?) villages, reinterpretations of Leng (like this excellent one by Laidlaw, aberration colonies, or perhaps a submersible that preceded the Spelljammer floating in a voyage of impossible discovery....
All good.
This thread unearthed by Anerta might prove useful inspiration:
http://community.wizards.com/go/thread/view/75882/19558806/Layers_of_the...
One of my favourite favourite realms detailed in that thread is Rip's page four submission "The UrVeel Bazaar." I just love everything about it and also want to draw nothing but UrVeel traders for the rest of my days.