Yeah you could think of it like that, a ‘slot’ for choosing what card borders you want, a ‘slot’ for which armor appearance or hair or face that you want. But I was going more for retro- stuff that they already paid artists to make so it would cost nothing for the assets, just the cost to program and implement the ability to change between them. Like if your hero could be Elspeth. Maybe slots too as well. 
As long as they are competatively priced and not $50 each, because then of course they won’t sell at the wrong price point. In the past few years that i’ve been playing, I don’t think I can recall ever seeing a sale on the Lapina or Dwarf or other items even during holidays. 