Change Black Macbook Pro screen to something cool when music is playing?

Solution 1:

With iTunes in foreground, either press ⌘T or select View > Visualizer, choose the animation, and select View > Show Visualizer.

The visual effect will change with the music: enjoy!

Solution 2:

On your Mac, open up System Preferences, then:

• Select Screen Saver in the menu bar
• Scroll down in the left-hand gallery and choose iTunes Artwork
• In the bottom-left, you can choose how long after you stop interacting with the computer that you want the screen saver to start by clicking the dropdown labeled Start After:.

This basically has your computer, instead of going to a black screen after inactivity, display your iTunes album covers, from which you can play these albums by simply clicking on their respective covers.