The following sites all contain collections of public domain images suitable for use with Web pages. These images are not subject to copyright restrictions in most cases.
Microsoft have an excellent gallery that contains just about everything you could need to get a Web page started. High quality images.
An impressive collection of art work which unfortunately seems to be an Internet gypsy. Nicely categorised for reasonably fast access. Possibly the biggest variety of animated gifs available.
The Icon Bazaar is maintained by a character called Randy Ralph. He does his best to sort hundreds of icons into meaningful categories. The site is very popular and subsequently quite slow to access.
Pam Bytes is a collection of original backgrounds, arrows and other miscellaneous icons produced by Gibson Grafx. All are of professional quality and file sizes are appropriate for Web pages ie: small files!
Can't get enough clipart? This is the site for you. Access to literally thousands of images and image resources.