Speaking of that, are there new graphical elements you really want to implement in the polish phase of the game? I think the game currently is a very good example of how cohesive art design and gamefeel can carry the game on its own without the need for visual fluff. Even so, small additions like these that work within the current scope of the graphics engine are very effective at aiding immersion.
One thing I personally would love to see eventually is a gradual breakup and explosion of shipwrecks that actually become destroyed rather than merely disabled, like in Escape Velocity, along with flying, red-hot debris...
That's something I'd love to see, too. Whether it's something I'll actually be able to get to is another question

If there's ever time, shield graphics are something else I'd like to take a look at. David had also mentioned wanting to tweak some of the weapon and engine effects.
Overall, though, I feel good about where the graphics are at. Incremental improvements are possible across the board, but that's not something that ever stops being true.
@BrickedKeyboard: Right, what Gothars said

I'll just add that I don't want to spend time on a more expansive system if it ends up being replaced by the "real" one down the line, anyway.
@Okim: Thanks for the reminder, added to the list and will make sure it's possible one way or another. Also sent you a PM.