By way of background, General Haig led the Somme and Paschendale offensives in which tens of thousands of Canadian soldiers died. My theory is that the son/brother/father of the homeowners was part of those offensives and died under Haig's command. The various sources I looked at (e.g., the Canadian War Museum's page here) suggest that much of the criticism for the massive loss of life during those battles fell on General Haig.

So my question is: Is there any evidence in the historical record of people in Canada (or the Northeastern U.S.) nailing photos of people they don't like under their floorboards? Where did this originate? Was it a superstitious thing? Or perhaps I have misinterpreted the situation and it actually means something else; in which case, what did it mean?

Unfortunately, we have no information on those previous homeowners, so we cannot be more specific about the homeowners' culture background or culture (except that they were probably white Europeans based on the area the home was built).