For Humorous purposes University of California, Social Sciences and Humanities Library,Graphics page A nice and tidey site. Good for academic purposes. This is a index for search engines. Has list of of major search engines and another list by categories. Image and Sound is one category.
Music is another.
There are just too many sites out there to deal with otherwise. The powerful search engines seem a good solution. There is also a big problem of stolen images in many of the collections that we have looked at. A very small portion seems to be aimed at educators and education institutions. This is unfortunate as the Internet did originate largely with educational researches.