Defining KPIs and Metrics...

I'm currently building out a Test PMO for an insurance company. We have a long term, fixed-price contract with a vendor using a waterfall model.  I'm currently working on KPIs and metrics which I will use to tell the testing story, which means both technical and business comsumers will need to find value in them. I'm conducting targeted interviews atm  but am interested in hearing if any of you have had experience in this arena.  

What kinds KPIs / metrics have you found valuable?

What kinds of chatring / mapping have you found to be confusing?

What considerations would you want to address?

Any additional comments?