If you have no artwork for a specific game you could use the emulator name for a folder/path and any images in there will be chosen randomly.
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From
http://attractmode.org/docs/Readme.htmlARTWORK SELECTION ORDER:
From the artwork paths configured for the emulator (if any) and the previously scraped artworks (if any):
[Name].* (video, i.e. "pacman.mp4")
[CloneOf].* (video, i.e. "puckman.mp4")
[Name].* (image, i.e. "pacman.jpg")
[CloneOf].* (image, i.e. "puckman.png")
[Emulator].* (video, i.e. "mame.avi")
[Emulator].* (image, i.e. "mame.gif")
From the layout path for the current layout (layouts are located in the "layouts" subdirectory):
[Emulator]-[ArtLabel].* (video, i.e. "mame-marquee.mp4")
[Emulator]-[ArtLabel].* (image, i.e. "mame-marquee.png")
[ArtLabel].* (video, i.e. "marquee.avi")
[ArtLabel].* (image, i.e. "marquee.png")
If no files are found matching the above rules, then the artwork is not drawn.
If no file match is found, Attract-Mode will check for a subdirectory that meets the match criteria. If a subdirectory is found (for example a "pacman" directory in the configured artwork path) then Attract-Mode will then pick a random video or image from that directory.