Gimmicks and Monthly Specials

I don't offer collections/packages to add "savings or deals" to my pricing. I like to price via a creative session fee and then all product is a la carte. But I was thinking of adding in some monthly promotional deals/items.

Does anyone here currently do this?

I'm looking for gimmicks. EX: JANUARY - Welcome to the New Year! Buy any photographic print size and get a second print of the same size/pose for free.