1. Two generations compared
Here you can see that the new iPhone appears to not just have a larger screen than the iPhone 4S, but in fact is a taller phone overall.
2. Another comparison between last year's and this year's iPhone
If these proportions make it to the final product, it's clear that the new iPhone will be about the same thickness and width as the iPhone 4S, so it should still slip into your pocket just as easily.
3. The buttons remain the same
The familiar side buttons appear largely unchanged.
4. The new iPhone posing alone
Another beauty shot of the device; making the phone longer may not actually be due to the screen size increase, but rather to give them more room on the inside to pack in the A6 processor, LTE radios, and an even larger battery.
5. New connector
This appears to be Apple's new iPhone port. Unless there is some sort of $20 adapter that is sold, expect to have to buy entirely new docking peripherals if you upgrade to the new iPhone.
6. A shot of the back side
Here you can see the camera and flash assemblies. As a test unit there are no markings indicating whether the camera will be changed over last year's model, so we'll have to wait until it's announced (or for further supply chain leaks).
7. Remember, it's a test unit!
As a test assembly unit the small details are probably not as polished as the final retail version will be. In these images the home button doesn't seem to blend in to the body as well as past iPhone models, but that may change in the final production units. Likewise, the metal sides seem darker in these images, but that could easily be due to the test unit nature of the device, rather than an aesthetic design change from previous iPhone models.