Waiting for the videos, I think the best option would be black colored, in the minimalistic design (the one without the zipper, #3).
As the design of the tablet looks simple and minimalistic, a case with external pockets and other decorative elements would probably be more functional but would also appear cluttered.
Regardless, as these choices are often personal, I'd subsequently make all models and colors available in the store at regular price, so everyone will eventually be able to choose what they like the most.
Also, I can imagine some people wanting other types of case/sleeve.
- a cover case like the ones for iphone or other phones on Mozo's website (protective case for back and corners, better grip)
- a folding case (protection for the back and the screen when not in use, better grip)
I particularly liked these models, but I mention them only to help identify the type of cases I mean:
Back cover case for Iphone 6 (light oak)
Nokia Lumia 1320 Folding Case (Black)