Booty Calls hosts weekly events that reward you with useful in-game items and a hot picture.

To check the current available event, click/tap the Quests button on the bottom of the screen and check out the Events tab:

The individual quests lists the requirements, as well as the rewards they individually grant you.

The top quest usually requires you to gather certain event-themed items from completing dates with the girls (in the example above - Vibrating Brooms) and rewards you with the event's picture featuring its character.

You may also instantly complete these quests by clicking/tapping the Skip button and paying the indicated amount of gems.