I finally worked this one out through trial and error. It is not at all intuitive, and I have no idea how to do it any other way. Customise your desktop on a test account then run sysprep and boot into audit mode. Copy the appsFolder.itemdata-ms and appsFolderLayout.bin files from %userprofile%\AppData\Local\Microsoft\Windows to the system you develop your images on. Mount your install.wim file using DISM, and copy the 2 files into Users\default\AppData\Local\Microsoft\Windows Unmount the image. It's a PITA having to mount/unmount after each new addition to the desktop, but I guess this will become less frequent once we are all happy with the distribution image. If anyone knows of an easier method, please tell.