The range of perception that goes beyond the material also goes beyond the agreed-upon to a large degree, so looking for mutually-held reality about it is kind of a contradiction, like looking for proof that one person feel love for another. In this sense you could argue that the material universe is essentially an average of agreed-upon illusions; it's commonality is what makes it so atteactive and persistant. But the range of things that one sees in one's imagination, for example, is infinitely greater, and completely unproveable in physical terms. Is your imagination unreal? Only if you define reality as purely material. But imagination is the source of every major positive change in human history -- the ability to perceive something as it could be. Yet it has no "place" and certainly no "proof".

A