On MacDeveloperTips.com I wrote about a Python script that can be used to capture screenshots of iOS apps, overlaying the status bar so images have consistent results (no differences in battery, time, etc).
It requires no external image files. The data for the overlay statusbar image are generated on the fly from data stored within the script itself.
It will work for any Retina iOS device in any orientation and wouldn’t be difficult to extend to non-Retina devices.
It can handle statusbars with a vertical gradient background in addition to those with a uniform background.
If you prefer working from the command line, as I do, I recommend you take a closer look.