I was able to add a tile to the Windows 8 Metro Start Screen that, when touched, runs a batch file, following these instructions: How to create shortcut of a file in Windows 8 Tiles?. The problem is that it switches to the desktop to run it. I would like that it runs in the background and stay in Metro mode. Is it possible?
EDIT: I finally gave up and upgraded to Windows 10. In Windows 10 Tablet Mode, a batch file that is executed from the Start Screen will make all icons disappear during the time it executes, and once finished, icons appear again in a smoothly fashion.