If people want them and you can provide them, it's a business proposition. Your cozy idea is a fun one. People like hand made items and leather has a quality feel to it. Keep your invested time reasonable and make some extra bucks. I personally like your simpler, uncluttered designs. In advertising art the white space (un-decorated area) is as important as the design. Too much detail takes away from the design effectiveness. I think the idea has potential. Keep making them and see where it goes.
By the way, what does the seam side look like?