There are a number of ways to sell your custom tattoo designs. The first would be to open your own shop and try to create your own business. Although this can be quite a rewarding proposition, but is really very difficult and time taking. Also, finding a place on rent, buying equipment and furniture, hiring employees and incurring numerous other expenses make it a relatively expensive proposal. Even if the money is available to open a shop, it takes time to build up enough client base to make enough money to get established.
You could be the best tattoo designer in the world but if you don't get enough business, you won't succeed. Offering custom designs would be one aspect of your business that could help, but all in all, opening your own business, especially in today's economy is risky.
You could launch your own website to offer your services as a tattoo designer offering standard and custom tattoo designs. You can build the website yourself, or have someone build it for you, and then you have to figure out how to drive customers to it. This is not nearly as expensive as the traditional store at a physical location, but somewhat equally risky. It will take time for customers to find you and build up a customer base and in the meantime, you may not be making a lot of money.
As a website owner, you would be required to monitor your site frequently to see if you've received any tattoo design orders and many times, the customer won't wait if you don't have a collection of designs readily available.
One of the best ways to sell your designs is to register with an existing business online as a tattoo designer. All the expenses are taken care of by them and you just have to set your own prices and hours of work. Customers are already driven to the sight, look through the designs or start a tattoo design contest and select the tattoo, or tattoos, they find the best.
Joining an existing website that has a decent collection of tattoo designs in various categories, custom tattoos, and that allows hosting design contests makes life easier for a designer in a lot of ways. One, they already have traffic and have a set up that makes is easy for the customers to order designs/ stencils from the site. All you have to do is put your designs online and get paid when a customer orders one of your tattoos.
If the customer is looking for a custom tattoo design, or has started a design contest, the designer will be working with the customer to create that unique tattoo that the customer wants. The website you're signed up with takes care of all the administration of the site, payment processing, and delivery of the designs. They make your job a lot easier and as a designer, you can spend all your time and effort in creating a design to the best of your abilities.
Overall, the best option is to join an existing business offering tattoo designers the option of creating an individual account and letting them do all the upkeep. This would be the best way to sell your designs to the clients across the globe.