From what I remember from watching "Ace of Cakes", is that the Groom's Cake is very unique and personal to the groom. It reflects his unique interest and his favorite cake flavor. Most of the time they were a gift to the groom from the bride, and had a theme of one of his hobbies.

For pictures these may be helpful: Ideas for Groom's Cakes 1, Ideas for Groom's Cakes 2, Ideas for Groom's Cakes 3, Ideas for Groom's Cakes 4, Ideas for Groom's Cakes 5, Ideas for Groom's Cakes 6, Ideas for Groom's Cakes 7, Ideas for Groom's Cakes 8, Ideas for Groom's Cakes 9, Ideas for Groom's Cakes 10, Ideas for Groom's Cakes 11, Ideas for Groom's Cakes 12 (this one has 16 pages of pictures).

You can Google Image Search "Grooms Cake" and whatever you are really interested in and find cake ideas for just about any interest (that you are willing to share with your family and friends).