What Do You Do When the Ideas Don't Come?
Employ the creative process loop.

Chart created by Dubberly Design Office in collaboration with Jack Chung, Shelley Evenson, and Paul Pangaro.
It's the visual equivalent of writer's block, and we often assume it is something we have to ride out until that lightning bolt miraculously returns. I believe the problem is not a lack of inspiration. Instead, it is that the initial spark of an idea is so delicate, it is often shot down by us creative types before it has a chance to grow. Our ideas are subject to outside forces: doubt, distractions, fear of the work being derivative, technical complexity, lack of time, lack of discipline, lack of money. There is the need to have the "answer" before we allow the idea to reach realization.
So is there a way to sustain one's creative confidence and energy throughout the process, from spark to product, keeping a balance between not knowing and the tangible, visible progress?
Employ the creative process loop, which consists of three stages:
Observe: Watching, looking and focusing on any quirks of interest. Anything can spark a creative idea, from a stray hair on someone's sleeve to two people in a heated argument. The observation is typically recorded: sketches of the hair or notes of the argument. These in no way are the final pieces, but they are practices that set the idea firmly in your mind, as you might record a dream when you wake up.
Reflect: When you review your notes or sketches, which part of them hold your attention? These notes or sketches are valuable, unformed nuggets that may mean nothing until you look back on them. I have found that when I find time to reflect on ideas, it provides space to daydream, to further the idea in a non-pressured way.
Make: This is the hardest stage, and is one that requires the greatest discipline: articulating the ideas clearly and translating them into a tangible form that can be communicated to others. When created, you have a sense of accomplishment and a balance of visible progress. When you present this tangible piece, you begin the cycle again: observing the reaction, reflecting on feedback that was given, then creating another version.