1. Google Image Search
This Search Engine possible very often you use and represent the way of best to find picture from various source in the web. You can exploit it more effective if you use option advanced.
This Search Engine claim make an index more than million photo of creative common, public domain, GNU FDL and other assorted photo and picture without copyright, so that you can utilize the picture for free.
This search Engine have specialization in searching photo stock from various provider site photo stock
This site make an index more than million free photo from various source.
You can look photo and picture here with many choices, for example you can chosen black and white photo or chromatic photo.