While Windows 8 provided a simple control for using a favorite photo on your lock screen, Windows 8.1 expands that personalization by providing photo slide show capabilities from the lock screen. And you can pick photos from your local PC, SkyDrive, homegroup or home network too.

Turning the lock screen into an animated photo slide show seems like a fairly obvious addition. But there's some software magic happening under the covers as well: Windows 8.1 will examine the photos in the folders you've chosen for this feature and will highlight those that most closely match today's date. So for example, if it's October, you may see photos from Halloween or other October events from year's past.

(Lock screen slide show shot from Microsoft)

As you might expect, you configure this feature in PC Settings: Navigate to PC and Devices, Lock Screen to find the control.

By default, Windows 8.1 is configured to display a static picture as with previous Windows versions. To change to a dynamic photo slide show, change the option "Play a slide show on the lock screen" to On. When you do, the interface changes to display a number of options related to this feature.

These include:

Use pictures from. By default, the photo slide show will use pictures from the Pictures folders in SkyDrive and on your PC. But you can optionally remove these locations—just select one and then click the Remove button that appears—and/or add other locations, including those in SkyDrive, your PC, your homegroup, and network locations. The Photo picker that appears lets you add multiple locations at the same time as well.

Include Camera Roll folders from this PC and SkyDrive. Off by default, enabling this feature will add the Camera Roll folder from this PC and from SkyDrive (the latter of which is usually configured to automatically display photos from your Windows Phone and other Windows PCs and devices.)

Only use the photos that will best fit on my screen. This option is On by default and will attempt to use those photos that match the aspect ratio of your PC's screen.

Play a slide show when using battery power. By default, the slide show will pause while you are running on battery power in order to save battery life.

When my PC is inactive, show the lock screen instead of turning off the screen. This is On by default, and when left as-is, it lets your PC screen function as a sort of digital picture frame that animates through your selected photos instead of dimming the screen.

Turn off screen after slide show has played for. Set to "Don't turn off" by default, this option lets you configure the screen to dim after 30 minutes or 3 hours if desired.

If you do enable this feature, you may need to give it a while to cache the photos it will use, especially if you're using online or network-based picture sources. But you can test the feature by tapping WINKEY + L (to lock the PC) or by signing out. It's pretty spectacular.