Here is something completely different: https://github.com/gcb/mk6

you can "write" (or even read) the screen shot in very simple HTML5 (soon markdown) and a CSS file will magically make it kinda-look like windows/gnome/kde/osx/ios/android.

goal is both to have fully accessible "screenshots" in documentation and to ease the authoring for developers. Mostly because i was tired of having a VM with default vm themes just to create screen shots :)