Admin has spoken about this in the past - I was under the impression that all die-cuts should have a white background, however Admin stated that:
Either a white or a black background should be used, whichever one helps show off the die cut better.
Not a direct quote, but close and it conveys the intention (and the correction to what I had originally thought).
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).