Here's my suggestions:
1) I love your space stations and space ships, the textures are superb and the polycount is very reasonable (I like the 1k-2k range). It would be really cool to see a model pack with something like 3-5 different styles of ships, and then 3-5 ships of each style. For example, your two alien fighter ships are perfect for an insect-like race.
A neat addition might be to make a separate set of weapons for the ships, and create mounting points onto the ships so people who bought your packs could mix and match the weapons onto the ships (and in the game code).
2) I would love to see more space stations. Maybe some stuff similar to
Freelancer where they have docks that open and close (it would be a simple animation) so you can fly right in.
3) It would be awesome to see a model pack of just heads that had a few seemless talking animations ("normal" talking, "angry" yelling, "happy" joking) and then people could record video of the talking heads and use them in their games for mission debriefings or when you hail enemy ships, that kind of thing. The heads could be as many polys with as huge of textures as you wanted, since the models wouldn't actually be in the game.
Here are some alien pics from an online game I play just to give you an idea of some neat types of heads.
