So, you are looking into to customizing your Definition Center a bit. You are wondering if you can change the default background you see when logging into the Definition Center.
The answer of course, is yes. You'll need to log into the Definition Center with Administrative rights to make changes. Once you log in, select yourself in the top right, and then 'Administration & Settings'.
Among all the fancy Administrator options you have, select the 'Customizations' option.
Scroll down to the 'Home Screen' section, and the image you would like to see, (or have your stakeholders see), when logging in. Don't forget to hit the save button down at the very bottom.
Now you're all set! Fun fact: If you don't see your new background, it's probably because the site is cached.