The following are very basic, undeveloped ideas that have crossed my mind for possible Dragonstar campaigns. Dragonstar is a very cool sci-fi game using the "classic" races from D&D. It's published by Fantasy Flight Games and is, IMO, one of the best d20 products out there. As I write this, I am anxiously awaiting the release of their Guide to the Galaxy which will give detailed setting information (at this time, only the Starfarer's Handbook has been released).
Adventure Seed #1:
The adventurers are hired to find a crown "suitable" for a dragon emperor. Any of the House Overlords can easily hire the PCs (probably best to leave Mezzenbone out of it so that you can use the Drow Secret Police as antagonists). The only crown that is "suitable" for a dragon emperor (at least in the mind of the employer) is the "Crown of the Ivory Emperor" (see AEG's "Dragons" for more info). What happens if the players discover just what they're looking for? What about if the other dragon lords find out about the mythical artifact?
Adventure Seed #2:
The emperor's forces emplaced on the Empire's border with the so-called "Dark Zone" have recently come under fire -- by strange, squid-like creatures. At first it is -- not without merit -- thought that the Illithids have finally shown themselves. But the truth is far worse. How about some Cthulu creatures invading after their resting place was disturbed by the Empire's expansion?
Adventure Seed #3:
The Sects of the Reaper and the Destroyer have been sponsoring Blackguard organizations and attempting to unleash the currently imprisoned Tarrasque on civilization (the Tarrasque was imprisoned eons ago by. They are seeking artifacts (keys) to unlock the seven doors of the prison. Emperor Mezzenbone and the ISPD aid the Church Sects when they can (Mezzenbone has delusions of being able to control and direct the Tarrasque).
Adventure Seed #4:
Bazzrit is using the Black Hole Syndicate as a means of funneling an army of fiends into the galaxy. While the Raksasha continues other criminal operations, he focuses his attention on the smuggling of demons, devils, and infernals of all kinds from portals on Outlands worlds. He needs to be careful and seize control of the portals quickly (before the corporations do) to keep his operation concealed.