This is a very weird fixation I'm going to admit to you all, because I know I can trust you: I have a weird thing for trunk-area/size/volume diagrams. I love strange 3D ones, and I love simple, flat, 2D ones. And I have no good reason why.
As far as car diagrams go, these are possibly the most mundane and least interesting ones. Unless your life consists of ferrying around odd-shaped, non-rectangular objects (moose antlers, Moravian stars, collapsed geodesic domes) I can't imagine why you's care all that much about the shape of the luggage compartments ion your car. But I love looking at pictures of them.
Which may be why I liked this diagram from a 1958 Popular Mechanics so much. It has some of my favorite cars, too — Beetles, 2CVs, BMW 600, and the glorious Multipla.
Maybe there's another out there with the same strange fetish as myself; in which case, I say enjoy, buddy.
Also, now I'm wondering what people crammed in that BMW 600's tiny little luggage well. A pineapple?