If you want a pretty picture, just visit the Metropolitan Museum of Art.
The Metropolitan Museum of Art has put online 492,000 high-resolution images of artistic works. Even better, the museum has placed the vast majority of these images into the public domain, meaning they can be downloaded directly from the museum’s website for non-commercial use. When you browse the Met collection and find an image that you fancy, just look at the lower left-hand side of the image. If you see an “OA” icon and the words “public domain” (as shown in the example below), you’re free to use the image, provided that you abide by the Met’s terms.
Also, the British Museum has made 1.9 million images available.
Classy, not cheesy.