Just got a craft cutter and don't know how to use it/what to use it for? Want to test it but don't want to create your own designs? These are easy ways to get designs to cut.
Not free, but they're easy to get. Try searching for cards, to make something you'll always use. Look out for 3D, for something to assemble. I wish you could sort by anything other than date, though.
Chinese paper cutting
Chinese paper cutting is a traditional handicraft that features some very intricate designs - surely enough to challenge cutter and paper. Just image search for "chinese paper cutting", import the picture into your cutting software (pictures with only 2 colours are best), and trace the edges. Extremely easy to get patterns, and free!