Here is a galaxy test, based on this tutorial. Enjoy.
That's pretty good. Three things jump out at me, though. The center of the galaxy goes from regular spiral to "white out" much too abruptly; there should be a "soft" light around the brilliant center and I would make even that begin closer to the center than the brightness here. There are no especially bright stars in the spirals. While there is some suggestion of dark lanes, the appearance is still dominated almost completely by stars, whereas real galaxy have prominent dark clouds and glowing nebulae.
This is a reasonable suggestion of a galaxy, but the complexity of even a fairly simple "classic spiral" (ignoring bars, significant irregularities from galactic interactions, extra-galactic clusters and satellite galaxies, and other such complications) goes well beyond what is shown. I think this could be the start of a very impressive galaxy, but it would take a lot more work to really look authentic. Which may or may not matter, depending on your purposes. As a map, rather than a picture, it is quite reasonable. A navigational display might ignore actual brightness of stars, interstellar matter that has no real interest to the pilot, etc. However, in that case, I would tone down the central brightness even more, since it would be adjusted for clarity.