One of the techniques I'm teaching my downline today in our Luv 2 Stamp Group meeting is how to use the brayer to achieve backgrounds like this:
You can click to view it larger.
These were all done by brayering the cardstock first with Barely Banana, then Summer Sun, then More Mustard and then some Really Rust. Each time you add a color you brayer less and less of the piece of cardstock. The "sun" was a mask I punched out of a post-it note. I stamped the "Inspired by Nature" image in Basic Gray after I brayered, but you can stamp first if you wish.
I was inspired by fellow Advisory Board member Tamie Ackerson's card HERE. She used sponges, and I used a brayer.
I hope to have a video or a tutorial soon... this is a great technique!