Brand driver is quite acceptable, but if several items are listed I think you might be better with a plural.

"How do companies express this notion across product and environmental design, manufacturing, merchandising, marketing, operations and human resources to deliver a robust brand experience and succeed in the marketplace? First, they must do their homework, assess the market and align their core competencies with the needs and desires of their target customers. Importantly, they must distill all of this learning into a clear definition of what their brand stands for--its vision, values and promise. Or, what we call a "Brand Driver," a succinct collection of words, even a single word and/or picture that telegraphs the core (big) brand idea. A "Brand Driver" that is so elegant in its simplicity, everyone intuitively "gets it" and can then "get with and behind" it in actuality. Herein lies the bellwether from which all customer and internal brand decisions are driven."