Probably the best site (quality images, supplied by DND so no copyright issue, usually with a full caption so you know the context, on an operation basis, with links to all three branches) is:
http://www.forces.gc.ca/site/gallery/index_e.asp
A site that also falls in the "safe and useful" category (usable and DND-sanctioned) is:
http://www.combatcamera.forces.gc.ca/common/combatcamera/find_e.asp
Of course, the various branches tend to have their own thing going on, such as Army's ...
http://www.army.dnd.ca/Land_Force/English/home.asp
And beyond that, even the particular brigades and fighting groups have identity sites (where you can sometimes find excellent pictures), for example ...
http://www.army.forces.gc.ca/38cbg_hq/Headquarters/units_page/38cbg_home.htm
If you are lucky enough to be a reader of this blog who's in the Canadian Federal Government then the above links might be useful for your work.