Optimism. Patience. Willpower. Flexibility. Lack of Ego. Vision.
Notice I didn't say creative. People with a creative instinct, as opposed to a creative impulse, are the ones that will set you free.
Why would you want a creative manager that isn't creative?
I've had a ton of creative managers that are top of their game in design, copywriting, web development, account management, and even project management. All of them had empathy, intuition, and logic in equal measure, and understood how to look at the work and speak to it in a way that made it sing.
However, the best creative managers I've ever had all shared one characteristic: the ability to properly identify and make use of the creative thinking of their staff. Whenever possible, they don't impose -- they expose. They cede control of details to ensure the big picture is still pleasing when the last few strokes are painted into place.