Digital Content -What tools to use to test quality

I just started working for a company where they do digital content for display stands.
What tools can I use to test the quality of images and videos or just content overall.

This is a tough question, not a lot of embedded stack engineers hang out online, and the tools they use are often pretty dear.
Firstly, welcome to the Ministry of Test, hope you do find some answers, I can only speak from my limited experience, that this really is a tough cookie to crack. I worked in a similar field before and we really did do a lot of “wetware” type testing.
A lot of things you think are obvious solutions turn out to be high cost in many ways.
• And so simple metrics like frames per second output via debug traces in the app code are your best starting point. Log these over time and compare them for release to release using a “golden” hardware test rig that nobody is allowed to modify. You coudl even graph the performance of each release onto a powerpoint and leave it up on a screen
• Build up a collection of “adversary” video content sources. Basically videos that are hard to render, build up a collection. Ones that either use slow colour gradients, or rapid motion, cartoon clips with crisp colors and lots of motion, nature clips with large vistas that are pleasing to the eye are also good candidates, and then unusual videos that do things that mess with luminance. (the human eyes is good at detecting lightness/darkness anomalies and often ignores color errors)
• Run AB comparison tests, once again another wetware test where you set up 2 displays side by side but don’t tell the user which display is running which version of app. Get them to choose which display is best in a series of small very short tests by filling in a clipboard. Swap the screens throughout the test at various set points, and offer them a snack for their time at the end. Then add up all the test sheet results. Even adjust the light in the room as part of the test. Oh, and obviously get a light and color meter when you do run this experiment. Make sure you control the room in every possible way, no noise, no outside light sources at all.
Hope that is a clue, and also you do not have to test everything, choose a focus. Also, be prepared to stare at screens for a long time, and observe, and also be prepared to lug equipment around and stop people from stealing it.