You can do your own merchandising. For people who just like character design or who don't want to create a story or world for the characters they draw, a good idea is to sell prints and merchandise like mugs, pillows, phone cases, stickers, t-shirts and greeting cards. Check out places like Etsy or print on demand sites to see what's being done and how you can bring something new to the table.
There's also fashion design or perhaps personalized scrap booking art. You could cartoon someone's kids and print sheets of papers and stickers for their scrapbook. You can print your own shower curtains and fabrics now too. You could do an entire home in "storybook style" if that's your thing. I'll just mention that I've never seen any storybook style car decor that wasn't Disney related. (Tinkerbell window decals and so forth.)
"Design" is a pretty big tree, and you could explore some of it's branches. haha