Some of these decks are just silly.
If you make it, they will buy it.
I have an idea for a Tarot deck myself. Of course the big hold up is indeed the artwork. Painting the artwork for 79 cards is no small task. Especially for a person who isn't a quick paintner.
Although I'm sure you've noticed that some of them are nothing more than stick figures draw by hand. A lot of them have really simple artwork that I could do myself. Almost like 'cartoon' drawings.
In fact, the most popular Rider Waite deck isn't really difficult artwork. It has a 'cartoon' quality to it with fairly simple colors etc.
I have a few tarot decks myself. Including Rider Waite, Lewellyn Tarot, Mystic Faerie Tarot, Renanessace Tarot, and Dragon Tarot. I've been thinking about getting the Buddha Tarot just because I know enough about Buddhism for it to be meaningful to me.
I actually use all of these decks, depending on which one calls to me for a specific situation.
The artwork in the Buddha Deck is pretty simple actually. It's just line art filled in with solid colors and not much shading or detail. I think I could draw cards like these:
The Mystic Faeries Tarot has more detail and shading, but I'm getting close to being able to paint like this. It's just more time consuming.
And I'm working toward being able to paint even more detailed pictures like done in the Llewellyn Tarot. These are quite detailed with lots of shading and color tones. But that also requires much more time spent on each painting. When you're talking about painting 79 cards that can add up pretty quick.