I'd say, if it's a valid release with a disc in it, it would count as a variant. If it's a promotional box art in an empty case (like what GameStop uses to sell preorders), then that would not be a variant of the game and doesn't really belong.
The spirit of VGC is to catalog every version of every game out there.
Our goal is to eventually house the largest and most accurate video game database on the Internet. Each listing includes box art, descriptions, item numbers and more. We cater to the hardcore collectors by creating an individual listing for every known variation. Does one game have a few box art variations? We'll list them separately so you can be a thorough as possible with tracking your collection.
If we are unsure about an entry we should try to research it before jumping on the merge button.