Any suggestions where I can find non copyrighted pictures?

Answer 1

From your head.

You have a brain, why don't you create some pictures?

Answer 2

Ones you make yourself of course.

There's a company that puts out books of old artwork like engravings and drawings that are so old they've gone into public domain, it's Dover Publications, they have a website. You buy their books and can use the pictures they sell (check to make sure the books ARE copyright free, they do put out some that aren't).