Apple includes a number of built-in screen savers in OS X that can show iTunes artwork, photos from your iPhoto library, and decorative patterns, among other options. One of these is the “Message” screen saver, that might be attractive to some because it offers a more subtle option of displaying a quick text message (which by default is your Mac’s computer name). You can leave this default text as the message to use, but if you want you can customize it, and even spice it up a little by adding emoticons.

To edit the Message screen saver and add emoticons, you will first need to enable the OS X Character Viewer, and then edit the message text:

1. Open the Keyboard system preferences
2. In the Keyboard tab, check “Show Keyboard & Character Viewers in menu bar”
3. In the Input Sources tab, check “Show Input menu in menu bar”

With these done, you can access the new input menu and choose “Character Viewer,” which will display a panel of unicode text characters you can use for any text field that supports unicode. Among the many greek, math, music, technical, and language symbols, you will see a category for “Emoji,” which will have all of the smily faces that are available in Messages and other similar apps.

Now you can edit the Message screen saver and add one or more of these emoji (or any other symbols you like) to the message text:

1. Go to the Desktop & Screen Saver system preferences
2. Click the Screen Saver tab and choose the Message screen saver
3. Click the “Screen Saver Options…” button.
4. With your cursor in the text field that pops up, double-click a desired symbol in the Character Viewer panel.

When this is done, the clicked emoticon will be entered in the field, and will show up on your screen when the screen saver starts. Unfortunately you cannot add any other images to this field, but any fonts characters and images you have installed on your Mac are valid candidates.

Why use a screen saver?

While the need to “save a screen” from physical phosphor coating burn-in damage is not needed for modern flat panel displays, screen savers still have their utility to prevent LCD ghosting, where LCD pixels may show a reduced response over time when a given pattern is displayed and result in a similar-looking burn-in (though this is reversible by displaying all while or all-dark patterns for a period of time). More commonly though, screen savers are useful as an indicator for a system that has been idling long enough where it is about to sleep or invoke a screen lock. Lastly and perhaps most importantly, however, screen savers are simply decorative and fun.