Well, this always comes to the question of coolness versus realism. The backgrounds currently in use (lightspeeds cool ones and such) are impossible. Regardless, they are cool. But.
I think that it would be very much possible to create very good-looking starboxes by using just stars, and planets of course if one happened to be conveniently nearby. For example the Sol system simply doesn't have any colorful nebulae around it, but the sky with stars is cool in itself. Of course you would have to have the Milky Way visible. Add to that differently colured and sized nearest stars (red Betelgeuze and orange Arcturus, bright Sirius and blue Vega and Regulus... you name it. Most star systems would be like this, quite similar in starfield itself. Planets should take a greater role in backgrounds IMO. Everything would be centered around them anyways in normal systems.
But then there could (and probably are, too) some star systems that would offer really spectacular views. Mostly I'm talking about systems inside or next to star clusters. Having a star cluster near you could fill the whole sky with relatively bright stars and gas illuminated by the stars. For example, take a look at the Pleiades, or M13 cluster at Hercules constellation:
M45 Pleiades Open Cluster
M13 Hercules Cluster
Even in the wildest backrounds we haven't yet had anything like these IMO. Of course the gas would not be quite dense - locally the space is practically just as transparent as in solar system. But in the long run, being inside a nebule would definitely create a subtle shade of color to background darkness. The colour of a nebula is defined by the color of the star that illuminates it.
It would be very interesting background in a mission inside a spherical cluster...
Galaxies and nebulae would not be nearly so impressive as these. Of course, if GTVA discovers intergalactic subspace travel, there could be some missions situated in some more dense cluster of galaxies... something like this:
Abell 1689 Galaxy Cluster
Clusters FTW!