Well, personally, I had the "bliss" image from the Windows wallpaper collection in my head while I was writing this. But I'm cognizant that most of the photos of hillsides I took in Ireland had sheep in them.
I wonder if that would still be true, though, if "bliss" wasn't a default Windows wallpaper. In other words, you're still referring to common pictures, you're just particularly biased to one in particular that you've seen a lot.
I haven't done the experiment, but I'd posit that if you walked up to a group of 8-year-old children, gave them crayons, and asked them to draw pictures of "rolling hills", a significant portion would add sheep, cows, flowers, or some other details—even though a majority of rolling hills in the world don't have any of these features.
I haven't done the experiment, but I'd posit that if you walked up to a group of 8-year-old children, gave them crayons, and asked them to draw pictures of "rolling hills", a significant portion would add sheep, cows, flowers, or some other details—even though a majority of rolling hills in the world don't have any of these features.