Extracting AppImages

All recent type 2 AppImages (created with an appimagetool newer than Nov 15, commit #51fdac2) can be run with extra parameters, all with a naming pattern *--appimage-<something>. You can list them all by running it with --appimage-help:

./WhatEver-x86_64.AppImage --appimage-help
AppImage Options:
  
   --appimage-help                 Prints this help
   --appimage-offset               Prints the offset at which the embedded filesystem image starts, and then exits
   --appimage-extract              Extracts the contents from the embedded filesystem image, then exit
   --appimage-mount                Mounts the embedded filesystem image and prints the mount point, then waits until it is killed
   --appimage-version              Prints the version of AppImageKit, then exits
   --appimage-updateinformation    Prints the update information embedded into the AppImage, then exits
   --appimage-signature            Prints the digital signature embedded into the AppImage, then exits

If you run ./WhatEver-x86_64.AppImage --appimage-extract, the AppImage will auto-extract its contents into AppDir (currently as a sub-directory squashfs-root in the current location. Then just change into that directory to look around and see what elements the AppImage is composed from.