Sixteen years and mostly missionary ? Well, at least you're doing it, so that's a nice, pleasant start.
If you wanna spice it up, how about the shower, the kitchen table, the couch, the floor, against a wall, on top of the washing machine, in the car ...
Tell her that you're not necessarily too keen on the idea of the strap on (if you're not ...), and try this instead:
Both of you write ideas on some nice pieces of paper, put them in a jar, and one of you pick out a note every night to decide how you're gonna do it.
There must be at least 500 different ways to please each other. Have some fun !!!