When I look at pictures of many wine cellars, I see alot of "presentation shelfs" - that is, a middle shelf that used to show off the bottle of wine. They are usually at an angle so it is easier to see the bottle. I dont' understand why this isn't considered improper storage since the cork could dry out? Is there something I am missing or do people just put empty bottles in those shelves?

I've noticed those also. Although I don't have such a cellar to prove out, I would imagine that as long as its at an angle, the cork would remain in contact with the wine. You just need to get the bottle at an angle such that the air bubble drops below the shoulder.

Properly done, the angle is slight and the bubble is, in fact, at the shoulder. As you might guess, this is safest with bordeaux bottles with normal fill levels. I just went to look, and in fact, I have a 1962 white Bordeaux ("Y") with a low fill and I can just see the upper part of the bottom of the cork. Of course, the motivation to open a '62 white bordeaux is small, but I probably wouldn't keep old Burgundies on that shelf.