I would answer this as, if your residents enjoy it and it's not a hardship for you, why not?
The property I live at has balconies and every year tenants put up decorations on their balconies, and I think it's great. It looks festive, fun and everyone enjoys it.
Going further into this, for every office closing notices are sent out stating that In Observance Of [take your pick] the office will be closed, etc. and insert one of those clip art forms for Labor Day, Memorial day, Christmas, new year, whatever the holiday. The favorite among the residents for labor day was that 40's era poster of the woman who has a kerchief around her hair, her shirt sleeve rolled up and arm flexed with the caption "we can do it". Rosie the Riveter!
Several years ago I watched as a naval base in Fairfield CA was embroiled in a heated dispute in which some asked (demanded) that the Christmas display of the manger/baby, wise men,etc, not be allowed (it was a huge display). The base ruled on it, said all are allowed to participate in their religious holiday. The manger has been displayed for the last 40 years and is staying.