@theotherdan

Thank you. This was caused by the environment though. I was booting into PIXEL desktop before launching EmulationStation. This configuration prevents quite a few things to function as expected.

This is already supported if you are running the master branch (which can be installed using the emulationstation-dev module). It looks for a subfolder named 'images' within the roms folder. It will find images, marquees and videos using the following paths:

<rom-director>/images/<rom-name>.(jpg|png)
<rom-director>/images/<rom-name>-marquee.(jpg|png)
<rom-director>/images/<rom-name>-video.mp4