About 2 months out from the release of every new iPhone or iPod we normally begin to see leaks from case manufacturers that, at times, give us hints about the look of the device. Today’s leak comes from Mobilefun, a UK site that is heavily into iPhone accessory and case sales and shows what appears to be cases designed for an iPhone with a larger screen and a lozenge-shaped home button.

The images come in two forms, with one being a sort of design document, used for specifications in making cases, while the other is an actual physical prototype. Both of them exhibit some physical details like buttons that have been moved to the opposite side and a curved back reminiscent of, well, the iPhone 3G. Many of these details sound much like rumors posed by This is My Next, a few weeks ago.

iPhone 5 case2 520x528 Possible prototype iPhone 5 cases show larger screen and home button

The home button opening of the cases depicted here is also an oblong, “lozenge” style opening, which suggests a touch sensitive home button. It’s impossible to tell whether it would be a physical button or not, but I’d say that it is more likely to be a regular push button than a touch-sensitive capacitive job.

In the CAD mockup you can clearly see that the screen has been enlarged to an apparent 4″, minimizing the bezel, especially at the edges. The volume buttons have also been moved halfway down the side, perhaps to make it easier to use them as a shutter release for the camera, a feature of iOS 5.

IP5211 Possible prototype iPhone 5 cases show larger screen and home button

The curved back is the most interesting detail to me though, as it simply screams ‘curved glass’ to me. Ever since the news leaked out that Apple had purchased machines used for cutting curved glass, almost every site out there has been shopping rumors that the next iPhone will have a curved glass screen. I’m 100% positive that it will not and, from the very day that the machinery purchase came to light I’ve been convinced that if Apple is including curved glass in the iPhone at all, it will be on the back of the device, not the front.

If these case designs are accurate, the back of the iPhone 5 will go back to a curve, which I feel is much more ergonomically sound than the current flat-backed design of the iPhone 4. If we do see a curve, it very well may be an aluminum back, as some have supposed, but my money is on glass.

Of course, for every case design that accurately predicts the appearance of an iPod or iPad product, we also see dozens that are instead mockups based on rumors or design documents that change significantly before the product is released. So I would note this as an interesting rumor but I wouldn’t start basing any solid ideas as to the look of the next iPhone on it.