The British Library on Flickr The British Library has uploaded over a million photographs and scanned images they are all in the public domain
http://www.imagesofengland.org.uk/ Images of England is a ‘point in time’ photographic library of England’s listed buildings, recorded at the turn of the 21st century
http://www.francisfrith.com/ Francis Frith was an English photographer who produced postcards of many places around England for the tourist trade.
Britain from above 1919-1953 A collection of aerial photographs of Britain
Royal Museums Greenwich Picture Library A collection of maritime images
The original entrance to the White Tower, Tower of London. Image courtesy of wikipedia.
The following items are available for use at the State Library of South Australia. They will give you valuable information on how to date your photographs using clues like hat size, facial hair or lack there of, the shapes of sleeves and collars and the length of a dress's hem.
Fashion at the races, 1912.
More information about this image.