In the 16th century, Rikyu was a tea master for the warlord Hideyoshi Toyotomi, a difficult and powerful man. Hideyoshi heard of the wonders of Rikyu's garden of morning glories and expressed a desire to see the flowers. As a result, Rikyu invited the warlord to tea. When Hideyoshi arrived and walked down the path to the tea house, not a flower was in sight. Upon entering the tea house, Hideyoshi saw a single, beautiful morning glory displayed on the alcove. Rikyu had cut down all the other morning glories so that full attention could be focused on one single blossom.
Like the morning glories, the beautiful nebulae should be an infrequent experience, islands of beauty in a sea of stars. I personally think that those beautiful nebula skyboxes that have been featured in the screenshots and later videos should only make up around 5% of systems, with a small percentage being much more dusty, and a large percentage having little to no nebulae whatsoever. Though this exact ratio will probably need to be tested.
This will mean that at least skybox-wise, most of the game will be less beautiful but it will make those few systems that much more gorgeous in contrast. They won't fade into "whoop dee doo, pink nebula #29378" but will always give a player that "Wow!" feeling when they come across one, even if they've played for a thousand hours.
Even then, when nebulae are rare, they may still be taken for granted. That cannot be permitted. The only real way for them to always be noticed by even a veteran player, is for them to actually mean something, to have an effect on gameplay or to convey broad information about the system at a glance.
Just as a couple examples of possible ways to make the skybox more than just pretty:
A rich and beautiful Nebula will have a small, but noticeable, effect on your scanner range and on the space-drag coefficient. Whereas in that empty sea of stars your Long Range scanner is 500,000u, in a nebula, it's 400,000u.
Space-drag isn't real except that Josh says it's so. We don't want drag to affect combat speeds very much, but it should affect larger ships, going at cruising speed; The faster you go and the bigger you are, the greater your drag. The presence and density of a nebula is just a multiplying coefficient of that drag, so in open space the coefficient might be 1, in a sparse nebula it might be 1.2 and a dense nebula, 1.5.
When skyboxes have an affect on gameplay, even if small, it can be important for different strategies, so it makes them always worth paying attention to.
Just a thought.