Rotating Banner

That it how the banner rotator works: It shows one random banner per request, not a 'slider' with all banners.

If you are looking for a 'slider' you can try to use the built-in webpart 'Content slider' or use a javascrip/jQuery based slider which you feed using a repeater (take a look at this solution: http://stackoverflow.com/questions/18041542/how-to-jquery-slider-in-web-part-kentico)

regards, Felix

If you are using a slider banner - I like to create custom page types for the banner then use a repeater to show the banners. You can then use jQuery or any slider script to create the carousel / slider effect.

Having the page type allows you to create any structure for that page, then the editor can easily add that page type to the content tree and add the content into it.

Creating page types
Create transformation for the page
Displaying the data on the page
Slick slider