Easter
Easter or Spring portraits are sure to be a hit if you use creative props. Inquire at your local pet store---most of them will let you rent bunnies if it helps promote their business as well. Buy a suitable backdrop that fits your theme---a meadow full of spring flowers or any pastel themed scene is appropriate for the season. Children with be intrigued with your borrowed pets and getting just the right shot shouldn't be a problem.
Fall
The Holiday Season takes off in the fall. Leaves and foliage are a natural and fun element to use as a backdrop. Schedule your clients for outside appointments in a favorite park. This is a great way to catch unsuspecting children at play. Bring plenty of business cards when you are shooting on location as passersby may be interested in your work.
Christmas
Christmas is the biggest holiday of the year for most families. Have several options available for your clients to choose from. A wintry forest backdrop complete with artificial evergreen trees for props and simulation snow is an idea. Have an old fashioned sled available as a poser and you've created a winter wonderland. A black backdrop with clusters of poinsettias in varying heights makes for a striking portrait. If possible keep several red articles of clothing in different child sizes to coordinate with your poinsettias.