Flex your Creative Muscle!
There are a multitude of artists out there who want nothing more than to use you for a wall on which to paint their wildest visions, or make their latest idea of a political statement, etc. It's not that they are mislead or wrong to desire this approach, but it stands in the shadow of what murals are really all about.
Whether your the owner of a grocery store with a large blank wall, or a homeowner with a dining room wall that has no windows, a mural begins with you. You may not have a clear understanding of what would please you, or any idea of how it might look when it's finished. But a well directed series of questions asked by a creative mind can usually fish it out of you.
Then, armed with that information, the muralist should be able to translate your input into a cohesive project with all of the flair and style for which you chose that muralist in the first place.
Believe it or not, murals that are to be painted on the outside of commercial buildings actually belong to the community. Their design should encompass local history, predominant ethnicity, local concerns, etc. In fact, in most cases the building owner is merely loaning his wall to the cause/project. And in most cases he/she is rewarded for doing so with increased patronage or simply accolades from their community. In fact, murals of this type are commonly funded by groups, individuals, grants and other sources.
The point is that the content of an outside mural must be endured by the local community. It would be unfair then, to paint subject matter that is foreign or uninteresting to them.