I recently fashioned some shaving brush holders out of some huge brass nuts.
Fortunately, the brushes I have, have a variant on the internal diameter of the nuts so they fit.
I think they look rather cool... (if I do say so myself)
Let's see what ingenious ways you have found to store your brushes.
The holders do look cool, and save a bit of space, but I reckon it doesn't really matter whether you store brushes upside down or on their bases. One member on another forum even tested drying times by weighing brushes at regular intervals after use, and concluded there was little or no difference.