If you have a lot of old magazines, you can go through those and tear out images that interest you. Or you can possibly get a lot of old magazines at a book sale or the library.
If you don’t have old magazines, you can go online and find images that interest you. If you aren’t going to use them for anything except your private folder, then you can just google images and probably get thousands.
Or you can go to one of the sites that artists put their works on: fivver.com, unsplash.com, deviantart.com, and find a host of amazing images.
Pick the ones that speak to you, that make you laugh, that you would file under “fun/exuberant,” that make you want to write a story to go with the picture. Put them in a folder. Label them. Look at them when you need a jumpstart.
Or just go look for images that would go with your stories. These are not for illustrations, but just to help you think about your stories.
Or go look up colors and find ones that you associate with something. Pick the something first, of course.