Having taken a look at these images, and having a bit of a background in drafting, I'm inclined to call fake. In all probability, a high school student in an intro to drafting class came up with these and then proceeded to parade them around as leaks.
The dimensions are arbitrarily scattered with very little useful information. If you're only going to give the outermost dimensions of the device as a high-level summary, why include the radius of the corner of the screen on the iPod touch? If you're going to give the radius of the corner of the screen, why not give the radii of the corners that are actually useful to case manufacturers, like, say, the corners of the device itself? Why give a dimension starting from the center of the iPod touch's screen to the center of the home button, rather than starting from the top or bottom of the device? For that matter, there's no actual center line drawn across the middle of the iPod touch's screen, so while the dimension appears to start at the middle, you can't actually know, ergo the dimension is totally useless. Why give (what I can only assume is) a cross section of the iPod nano? Why mark the thickness of the iPod nano on the cross section rather than the normal side view? Why have the right edge of the thickness dimension go all the way down to the bottom of the screen? Why are volume buttons represented on the iPod touch image, but the hold switch is not represented on the iPod nano?
I could easily go on, but the point is that these images are of very little information to anyone who would have a use for them. Essential dimensions are omitted, and nonsense dimensions are included. The overall construction is also simply shoddy. I've seen actual Apple dimensions for their iPods (I think anyone can, just go to developer.apple.com and click "Designing cases for iPod and iPhone" at the bottom of the first page. I don't think you even have to sign in,) and they are done far, far more professionally. These images are useful neither to case manufacturers nor the manufacturers of the devices themselves. So again I suggest that the images are fake.
Edit: actually, upon further reflection, seeing as the school year just began, the person I suspect made these is probably actually just starting a second year drafting course and got bored while the teacher was explaining the disclosure.