Currently the tiled background in C2 does not support animations, if it was a Sprite you would simply change its animation to change its appearance, but in your case, it is impossible.
The solution is to use another tiled background object.
You may have created some events to scroll your tiled background or do other stuff to it. If you add another tiled background, you either have to copy-paste all the events applied to the first one, then replace it with the new one (right-click, replace object). The best solution however would be to create a Family for all your tiled backgrounds, then have your events work with this family so you don't repeat yourself.
Another solution, if you want to do it quickly, is to put different backgrounds on different layers and set one layer visible at a time.