Here are some homemade objective markers I made for 40k (or any other mini game I happen to be playing.)
It's a simple idea and I think they look great. A few of them even have a bit of metallic sheen.
The "2001" theme pretty much gives me license to sci-fi up any game. They could be energy portals, power stones, warp stones that randomly happen to rectangular-cubes, fuel cells, or just mysterious obelisks that appear to confound those who find them.