"Artwork" media field missing

[extracampine]

Going to the settings for the Arcade/MAME platform, the different media folders can be set (control panel, cabinet, marquee, etc). However there is no option to set the "artwork preview" (as it is called in MAME folder. The artwork preview is essentially a game screenshot with the surrounding bezel art, in an image file. It's one of the more useful media items to see what the original game looked like. Please include this image option.