You might try using a magazine, vid, or even another conversation as a jumping off point to comment on how this or that really turns you on and then, if you'feel brave enough, ask him if he'd try doing "that" with or to you....
Another possible way to get him going would be to tell him (in a sexy and horny way) that you had "the wildest dream about you and him..." and be sure to let him see that you're really turned on just thinking about it.
Really though, if he just won't kick down with seriously intimate and healthfully unpredictable passion, you may want to reconsider your marriage plans. Some folks aren't creative themselves but a lover with a wild hair now and then is a joy to them. Other folks are a little hung up about outcomes, responsibility, being blamed/ridiculed/damned etc... They need our help learning to let go in an emotionally safe place with no judgements etc... Often we can help them by example.
But also, sadly, some folks are just lazy. They may even know the joys of uninhibited, consentual adult play but they're just not motivated to expend any energy there- neither for themselves, nor their spouse. What a pitty and a damn waste of time! If your man is one of those...warn him once or twice then if he's still a nogo, run for your life.
Good luck, good love, I'm thinking you'll bring him around ...there's no medicine for blah fuck like rocking that fuck's world!