One idea may be to have a group of phrases you use often already in the form of a phrase such as : Thank You, I love you, Will you please__, Thanks anyways....etc.
Picture boards are great too, especially if you have the time/resources to print pictures of familiar things/people/activities.
You can also personalize them a bit by adding a border around the edge and using scrapbooking material ( on clearance at Hobby Lobby alot) Like if the person is a huge Nebraska Conrhuskers fan, or a fisherman, gardener,loves music, etc....pictures of loved ones.
Good luck and let us know how it turns out and any other ideas you come up with.
~Cindy