Just open Safari on your iPhone and go to https://www.dropbox.com/sh/n22ihqo5mh7it8z/_CVOar8jhZ Long tap on a photo and "save image". Tap the right arrow to view the next photo, repeat. All of the photos will be full size in your camera roll. Once in your camera roll: edit, tap all of the iOS screenshots, "add to", "add to new album", and give it a name. Now scroll through all the screenshots in your iOS 7 screenshot album. They're not full resolution, but are close enough to give you a good idea of what the apps will feel like, without having to install a risky beta which will expire in July and automatically send your phone into DFU mode unless you've upgraded to the next beta already.