Testing Expo - What would developers and other roles like to see?

The test function within my company is small, but growing.

A lot of our developers have come from backgrounds which lacked separate, dedicated test functions due to the nature of the products and services they were developing. This means that quite a number of the developers and other roles aren't used to working with testers and don't really understand what we do.

In order to address some of this, the test team are holding an 'Expo'/Showcase on what testing is and what value it brings, particularly in an agile environment.

My question to the non-test roles here is what would you as developers, etc like to see at this kind of event? What would you/have you seen which has demonstrated the value of testing and testers to you?

Thoughts welcome.