Try the AltaVista Media Finder. With over 17 million searchable images, audio clips and video files in their online database, chances are pretty good you'll be able to find what you're looking for. This last feature is my favorite. I clicked on the Visually Similar link for one of the pink roses and got some other nice pink flowers, a guy with funny shorts sitting in a lounge chair, and a picture of the South Park gang.
Computers are funny.
If you're after a sound byte from the Bugs Bunny show, or a video clip from Titanic, it's out there. Net is a search engine and guide to multimedia on the Internet. You can use it to find audio, video, images and animations related to Movies, Music, Radio, Sports and Television, News and Education. The site is organized in a way that makes it easy to find multimedia resources on websites that are relevant to your interests. Try out Scour.