Can this be done?
 

How hard would it be to display a simple graphic on the zoning screens, instead of a black screen?

I had in mind calling the zone map of the zone you are entering during the load, but other ideas could be done.

Can this be triggered serverside, or is this requiring the verboten client alteration?

Heh... why are you asking us? Verant is the one that makes the boring Loading, Please Wait.. screens :) We do not tamper with the client.