First of all you should be careful when you use a screensaver on a LCD. A pixel it's on when it's dark on a LCD. So if a screen gets black on a LCD like some screensavers do it can be damaged.

After all this problems there were invented CTR's more resistant to burn-in or with sleep mode. Sleep mode means that monitor comes in to a state like "turned off". But also there were invented many other solutions like games that when not being played change screen time to time or screensavers.

When screensavrs were invented they were very simple. They just blanked you screen setting it to full black. After that there where inserted many effects including sound and animations to make screensavers more entertainment.

And now we live in an Internet world full of screensavers of all types. You can find screensavers on any theme. If you like it you can just download it.