dslrBooth allows your guests to choose whether or not they would like to apply an effect to their photos. Alternatively, you can choose an effect such as black/white to apply to all photos without requiring user interaction.
To turn on either of these, Go to Settings, General, Effects and you'll have a list of effects that can get applied to the photos. You can either apply one of them to all photos or you can ask your guest if they would like to use any of them after the photos has been taken.
For your own custom effects, you can import your own LUTs.