Awesome style willow. Sci-fi will most likely get purchases as many people have use for it, including myself. If you need help trying to get a concept of what people like try looking up the following.
Dead Space 1 and 2
Mass effect 1 and 2
Maybe some halo stuff
Doom 3
Aliens vs predator (The new one)
Or maybe even reference some stuff off your husband. Also PWP does some awesome grunge sci-fi. So does HoriZon.
Some things some of the scifi things some of us are in the need for, are defiantly what you already started.
Doors (Not to many to select from)
Consoles
Segments
various entites: Chairs, tables, boxes ect
Holo pads, this goes in many different ways. Holo systems are really awesome and can really fill the universe a little, I have some links to some reference material.
Various things like that can get someones attention.
Reference:
Doors (Also goes with holo stuff)
http://img.photobucket.com/albums/v114/kakashi282/Lets%20Play/wmplayer2010-07-0705-04-59-14.jpg
http://fc08.deviantart.net/fs70/i/2010/074/d/b/Mass_Effect_2_Doors_by_BlackSheep64.png
http://imageshack.us/f/686/me20aa16af.jpg/
Segments:
http://images.wikia.com/deadspace/images/c/cf/25.jpg
http://www.xbox360digest.com/wp-content/uploads/2011/04/mass-effect-2-dlc-bioware-unveil-3-arrival-screenshots-4.jpg
http://screenshot.xfire.com/s/111411546-4.jpg
Holo system and consols:
http://www.thatvideogameblog.com/wp-content/uploads/2009/12/mass-effect-2-thane.jpg
http://www.supercheats.com/guides/files/guid/mass-effect/m6-sovereign.jpg
http://www.techdigest.tv/mass%20effect%202%202.jpg
http://images.eurogamer.net/assets/articles//a/7/1/5/6/6/6/ss_preview_1.jpg.jpg?slideshow=true
Here is some more reference stuff for various things:
http://www.visualwalkthroughs.com/deadspace/intensivecare/intensivecare.htm
Stuff like that will no doubt get peoples attention. Though this is just my 2 cents. Your work is always amazing willow, can't wait to see what you make!