I loaded it up with NES games. I have only put 25 SNES games on it since Lissette is worried that Nicholas will be overwhelmed. I put hundreds of NES games on it before she said something.
A big thanks to NZA for giving me his large collection.
The retropie has folders for the following (I didn't even know there were that many systems!):
amstradcp
arcade
atari2600
atari7800
atarilynx
fba
fds
gamegear
gb
gba
gbc
mame-libretro
mame-mame4all
mastersystem
megadrive
n64
neogeo
nes
ngp
ngpc
pcengine
psx
sega32x
segacd
sg-1000
snes
vectrex
zxspectrum
After putting together the first machine, I think I could put it together in about 45 minutes, maybe less since I have all the software now. I am still up for putting a machine together for you, Little Nemo.