many thanks!!!!!! worked like a charm, although it had a syntax error at first the function needed to be:

function RandomSlideshowItems() { 
   return DataObject::get("SlideshowItem", "", "RAND()", ""); 
} 

I guess I should do a few more basics! thanks for the rapid response.

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On another note is it possible to limit the amount of data objects that are pulled from the DB, i.e. I upload 10 images but only 5 random images are chosen to be shown in the slideshow?

The fifth argument is the limit.

Changing the code to this allowed me to display a limited number of images sourced from my uploads and chosen at random. The result is a slideshow which will always have varied content, perfect!

 function RandomSliders($num = 3) { 
   return DataObject::get("Slider", "", "RAND()", "",$num); 
}