I found this image source:
http://www.geograph.org.uk/
"The Geograph British Isles project aims to collect geographically
representative photographs and information for every square kilometre of
the UK and the Republic of Ireland, and you can be part of it."
The interesting part is that
a) They already have a lot of images
b) They're free :-)
(They talk about 'Creative Commons', but they seem to mean Cc-by-sa
http://www.geograph.org.uk/faq.php#opensource They clearly reject ND)
The not-so-good part is that they only are 800x600