One of the more popular displays for a collector’s man cave (or woman cave :)) is the baseball diamond or baseball field mural. You take a display case, put an picture of a baseball field in the back and then attach your 9 or 10 cards (depending on your DH sympathies) of your favorite players, one for each position on the field.
The cards theme could be anything. For example, a collage of your favourite hall of famers by position, the line up of your favourite team, the combinations are endless. If I were to make one, my first would be the 10 players I enjoyed watching play either on tv or at the stadium. The mural would look like this: