Clipart is a high quality images' resource. The page is not free but subscribing yourself there will give you the possibility of accessing to a great amount of pictures arranged between categories as the following: web graphics, fonts, clipart, photos, illustrations and photo objects. There exist other sites like this one. For instance, other two options are: Fotolog and Metroflog. The next are two links with more info about them:

http://hubpages.com/hub/fotolog_com
http://hubpages.com/hub/metroflog_com