You have the ability to create your own images or artwork and upload them into your games. We do offer free Crouton packets on GameSalad Academy.
http://learn.gamesalad.com/croutons/
Visit Marketplace for free and purchasable art, and be sure to check out our tutorials and templates (within the Creator) for assets you can use. The forums also have a category dedicated to discussing and sharing artwork.
http://marketplace.gamesalad.com
http://forums.gamesalad.com/categories/art-graphics