Recommended online collections and portals

Digital librarian - images portal for 'the best of the web' as A-Z listing.
Intute - portal for arts & humanities, health & life sciences, social sciences, science & technology.
Wikimedia Commons - search engine for a vast array of pictures & images.

ARKive Biosciences - images of life on Earth including film, photographs and sound recordings.
British Geological Survey - National Archive of Geological Photographs.
CalPhotos - a collection of 46,350 images of plants, fungi, animals, fossils, people & cultures, and landscapes & habitats.
Centre for Bioscience Image Bank Freely available images contributed by academics, researchers, Learned Societies, industry and individuals - copyright cleared for educational purposes.
ImageBank - thousands of free, copyright cleared, bioscience images for use by academic staff and students for teaching and learning.
NASA Images (LUNA) - 100,000 still and moving images of the history of space exploration and astronomy.
US National Library of Medicine (LUNA) - 70,000 images (portraits, photographs, cartoons, posters) of the history of medicine from the 15th to 21st century.
Wellcome Images - The Wellcome Institute Library of historical medical images.