How to promote the value of testing?

The test function I work in is small, but growing in size.

We are going to be holding a 'Testing Expo' for the company in order to inform colleagues at all levels what a dedicated test function does and what value they can bring.

Many of my collegues in other areas haven't previously worked with a dedicated testers (indeed a couple didn't even realise there was a separate test team).

As a test team we want to promote how testing adds value to a project, why testers are necessary and the skills and attitudes of testers.

So, can people suggest what would demonstrate the value of testing to them?

Our current displays/presentations are: 1) Tester mindset - how testers think differently to developers 2) Test automation - testing frameworks, demostration of the framework we have built 3) How testing fits into the development cycle

It would be immensely useful to get the opinions of people on here, but could I politely ask that if you feel the need to 'downvote' this, that you leave a comment as to why. That in itself could provide us with valuable feedback.

Many thanks, Iain