Disable -use_bezels,  and maybe disable -use_backdrops and -use_overlays.  Or delete the file in your artwork folder in mame folder.  Or change -artpath to not point at the artwork folder.
More info on these options in mame's docs folder, config.txt.
Don't know how to disable?  Which build are you using; mameUI was a different UI than mame, and it can be differently between the two.