1. They are original works. (If selling your work, you don't have any copyright violations).
2. They are tailored to your style or likes.
3. They are a way to jump start your creative process.
AND sometimes, maybe
4. They can be cost effective, but not always...
Making your own patterned paper is a great way to learn. When you start with a blank sheet and add patterns, you are engaging your mind. Sometimes, just drawing shapes repeatedly can springboard you into another idea or image. Making your own patterned paper is a great way to add to your arsenal and have paper that you can use for collage, journals and paintings.
I started with blank card stock and black acrylic paint. I did a few pages and was inspired, so I took out plain old printer paper and painted on some and drew with a black pen on others. I just played around.
My first foray was using all black and white images. I took the pages and made photocopies so I could add color and alter the additional pages. When I make color pages, I have them color copied. This costs more per sheet, so I am more careful choosing the image I want to stock up on.
Before I knew it, I had completed 23 pages! Here are a few...
Hip to Be Square