Gender reveal Christmas cards

So my husband an I aren't revealing the gender to anyone until we send out Christmas cards. We want to get pictures done(hopefully I'm showing) an I'm trying to think how in the picture we could reveal the gender. Originally I was just gonna altar the ultrasound an make it the color of the gender either pink or blue. But that means id be copying 2pictures per card(50cards!) so to only have 1photo copy I need ideas for our family Christmas photo to reveal the gender(: