This is my "Super Nintendo Entertainment System.cfg" file. Hope this helps.
# Generated by Attract-Mode v2.2.1-41-dirty
#
executable retroarch
args -L /usr/lib/libretro/snes9x_libretro.so "[romfilename]"
rompath /usr/local/share/games/snes/roms
romext .smc;.sfc;.fig;.swc;.SMC;.SFC;.FIG;.SWC;.zip;.ZIP
system Super Nintendo (SNES);super-nintendo-snes
info_source thegamesdb.net
import_extras /usr/local/share/games/snes/snes.xml
artwork boxart /usr/local/share/games/snes/boxart
artwork cartart /usr/local/share/games/snes/cartart
artwork flyer /usr/local/share/games/snes/fanart;/usr/local/share/games/snes/titles
artwork marquee /usr/local/share/games/snes/marquee
artwork snap /usr/local/share/games/snes/videos;/usr/local/share/games/snes/snap;/usr/local/share/games/snes/screens
artwork wheel /usr/local/share/games/snes/wheel