Three ways I can thing of

1. Provide services – logo, covers and packaging for digital and physical products.  You have to create profile and portfolio page in all free lancers website you know and can find. The most popular for quick job is fiverr.com and many sellers offering additional services there for top dollars.

2. Create a cool graphics and put it for sale on the sites like Envato and Graphic River. Another versions of this – create a bundle of marketing graphics like buttons, CTA, icons, headlines, inforgraphics etc and offer it for sale on JVZOO, ClickBank, Warrior Forum etc offering 50% comissions to affiliates. They will drive the traffic and sales – you will collectt the money and customer list.

3. Create a digital course on the topic of graphic design – not on how to use AI or PS, but on how to edit ready templates, how to create branding set, how to create a marketing bundle or simply do a “case study” describing exactly what you did on the project in paragraph 2.

All of them working but number 3 is most lucrative one.