Anyone can make their own paper wallet design. As long is there is no monetary gain in custom wallets using the image there should not be any issues as its no different than you downloading a picture yourself and printing it. Or posting it on Facebook with a meme attached to it. These pictures are all over the web, doubtful every person out there has rights to display anything about 300. Dev just make sure you don't host the images on your site and you should be fine.  But don't quote me on it.