Since 2008 Library and Archives Canada has been adding photos to a collection on Flickr. There are now 4,343 photos in 147 categories. Here's the direct link to the LAC collection.The most viewed are:
|Opening of the New Nitrate Film Preservation Facility||8,332|
|The Shamrock and the Maple Leaf||7,650|
|Sir John A Macdonald||6,100|
|Canada and the Second World War||6,014|
|Halifax Explosion 1917||5,797|
|Prime Minister Alexander Mackenzie||3,926|
|Vimy Ridge April 9, 1917||3,865|
|Prime Minister William Lyon Mackenzie King||3,617|
|Kodachrome colour images of D-Day and Normandy||3,606|
|Canadian Women and the Peace Movement||3,450|
This is a source for royalty free images so go ahead and use to illustrate your family history, but do credit the source.
Explore Flickr for many other sources, Canadian and otherwise, for creative commons licensed and no-cost images. For instance, the National Library of New Zealand just added 4,304 photos to The Commons.