Simple. You said the normal ones would be inapproiate. I guess that would mean a picture of a man and woman exchanging rings or something. I said just get a card without the picture. If it is so normal, then any old generic verse should cover it.
And a lot of greeting card verses are gender-specific.
My point is this: there is a place for a tasteful greeting card. It's an effective way to be polite, even if I don't approve of the behavior.