Raster format is also known as bitmap or BMP. They mean the same thing and are comprised of pixels, so when you enlarge them they become diluted. It's the most widely used clipart format and is usually all you need.
Kids bring home the greatest creations of macaroni, glitter, and finger paint. Unfortunately, the macaroni bits and glitter is soon all over the floor or eaten by the dog.
For creative souls that love teddy bear clip art, you should have no trouble finding what you need online. Either try the websites above, or search for some other sites that offer cute images. All over the web clip art is used, for crafts, and for scrap booking. The best is the free kind, so get as much free as you can by doing a proper search.