This page provides links to download a variety of different screensavers for your PC.  Installation is a simple matter of downloading and running the exe file. This makes the downloaded screensaver the default but you can easily go to your Windows Desktop and turn the screensaver off or set another one as the default. 

Most screensavers are collections of 30 high quality digital images with most of them having a size of 640 x 480 pixels.