adobe photoshop - How to produce a blurred abstract (frosted glass) background like this?

I have been seeing these blurred backgrounds all over the place, so I would like to know the exact steps how to reproduce something like this . What I can imagine, is that they first blurred an image/gradient with a gaussian blur. But there has to be something more to it, right ?

+) How do I correctly use a gradient instead of a picture?

Answer

I created a similar effect with the Gaussian Blur tool in Photoshop set to a 60 px radius.

Of course, you can do this with any photo where you like the color shifts, your sample reminded me of a beach, so I found a beach photo on Wikimedia.

Another way you can do it is by creating the shapes you want and then applying a Gaussian blur to them: