Here is a guide plus a script i made to get all your scummvm games to show in emulationstation (which is usually a pain).
Ok first unpack all you games to a location (lets say /home/pi/RetroPie/roms/scummvm)
Now go to console and start scummvm (type scummvm ENTER)
OK now Browse to your game directory /home/pi/RetroPie/roms/scummvm
You will see a bunch of directories with your games, now put the mouse over the “Add game” button and presh shift (keyboard). The button will change to “Mass Add” , just it ok.
Ok now your games are in scummvm press quit.
Download the script i provide to your /home/pi
Run it with : python ES-scummvm.py /home/pi/RetroPie/roms/scummvm
The script will generate dummy .svm files so they can be read by emulationstation.
Now in es_system.cfg make shure your scummvm section looks like this (notice the %BASENAME% instead of %ROM% and the .svm for the dummy files):
There was a typo in the joystick command. It needs 2 dashes not 1. Also the path looks like it is setup for running off usb, not the internal SD Card. I have changerd the entry in Emulation Station to the following and it is working. Might also want to update the wiki.