Right-click on the desktop and hit properties. Click on the Screensaver tab. Select your screensaver and hit preview, which will preview the selected screensaver. When the image you want appears in the screensaver, hit the Print Screen button. Timing is a neccessity in the last step. This will take a snapshot of whatever is on the screen at the time of pressing the buttin. Open up your preferred image editor and simply paste the image onto your canvas. Repeat for other images.
That is the only way I can think of doing it...
