One revenue stream that artists can create for themselves is affiliate marketing. More specifically, amazon affiliate marketing. When someone clicks on a link you provide and purchases something, you earn income from a percentage of that sell. This can be extremely beneficial if utilized correctly.
Create an account on Amazon and mess around with the user interface for a bit. Once you learn how to create link and use them, start adding them to your website and social profiles. Read the guidelines of the social sites to make sure it's ok to post the links.
How much you earn is going to depend on how creative you can be driving traffic and converting that to sells.