Several websites are dedicated to free clip art and stock photo images, for any theme. Examples are CanStockPhoto.com and Clipart.com. Both websites host a wide selection of clip art, including 1950s-themed images, for free to download.
Clip art and stock photos are, in essence, pre-made images created for quality and convenience, for any subject or theme. Not every clip art or stock photo resource is free, however, as some websites charge for the use of their clip art or stock photo libraries. These sets can be downloaded for a royalty fee, and after that is paid, the images can be used for various purposes.
Free images, or royalty-free images, can be found through various websites, including the ones listed above, with large libraries of images that are available as part of the public domain. These images fall under free use, and can be used accordingly. These examples of clip art can be downloaded and used in such things as PowerPoint presentations, emails, party invitations and so forth.
The difference between clip art and stock photo imagery is that clip art is mainly comprised of illustrations, and stock photo imagery is photography taken of real-life objects, or human or animal subjects.