I've definitely designed some fun custom artwork. After getting into the arcade hobby, I've found that I don't quite fit into the norm. The idea for custom artowrk came alongside building custom cabinets.
I just enjoy the amazing freedom of being able to design (or redesign) a cabinet from scratch. 30 years ago this would have been impossible. Now you can build what ever you want and print your own graphics with the tools and software available to us for amazing prices.
I will say that I think simple artwork is better. Drawing inspiration from classic cabs like those from Taito and Stern has been helpful. Those cabs are painted one color with a stencil of another color, usually just black. I like them because it is a simple geometric design and the company name. They are classic, and making artwork or stencils like this is very do-able.
The same thing goes with Williams cabinets. The artwork on Defender and Moon Patrol is a little bit more complicated, but it is still just one background color and two stenciled colors over the top.
What I DON'T like is the hodgepodge multicade artwork. For example, I don't like the artwork with characters from 50 games stuck on a modified Galaga or Donkey Kong side-art design. I think that looks busy and unoriginal. To each their own, but that I think that is worse than just using original artwork.
I certainly don't need to tell you what software to use. It looks like you've got that under control.

For stencils, I just cut them out on my CNC router from thin sheets of plastic or even hardboard.I also rout a 45 degree beveled edge on the openings for better results. And of course you can always have them cut out of vinyl at a sign shop.
For printing, I have a good friend who used to work at a printing shop, and they handle it for me. Just about any place can print on vinyl.
I originally looked into silk-screening as well. For me, it just didn't make sense with these kind of quantities. And since the artwork is original I am the one determining what the original media will be!
What kind of artwork are you doing?