It's worth doing a little search at the UK Archives photo stream on flickr.
http://www.nationalarchives.gov.uk/africa/ includes a small number of Zambian photos, apparently copyright free. Several are pre or just post independence.
How about this for a KK photo?
See also the collections for other countries - there are many from South Africa, and there is one of the "Southern Rhodesia Executive Council" in 1933.
Some aerial photos are quite interesting. What is this? It looks like the High Court in Lusaka, but I can't quite figure it out!