Tyrian, the vertically scrolling shooter! Remastered by LostGarden's Daniel Cook. Package includes all kinds of beautiful space-shoot-em-up stuff.

Jason Emery, the maintainer of the Tyrian source is still hosting a great fan page for the game: http://tyrian2k.proboards.com/

(When possible, link to blog post that discusses the original art collection like this:
"Remastered Tyrian Graphics" art by Daniel Cook (Lostgarden.com)