What "isms" would define or strengthen your culture? The software company Quicken is known for their "Quicken-isms" - catchy sayings that define their cultural norms in a shorthand way. Here are a few of their Quicken-isms: 

• Innovation is rewarded. Execution is worshipped. 
• It's not about WHO is right, it's about WHAT is right.
• You have to take the roast out of the oven. 
• The inches we need are everywhere around us.
• Simplicity is genius.

The meaning of some of those are obvious, but some need a bit of fleshing out. For example, "You have to take the roast out of the oven" means that at some point you have to stop planning and start doing...or you'll burn the roast.  

A fun twist on this idea is to hold a contest to encourage employees to generate their own "isms" they feel should guide your culture. You might even already have some characters at work who are known for certain phrases. One company has done this successfully, where the employee who coined the ism gets credit whenever the isms are displayed: "Never dunk your donut in someone else's coffee." -  Frank. Frank, in this particular case, was famous for using this expression which, in non-donut speak, means, "Tend to your own business before meddling in someone else's."