Simple and effective I think, this one. A combination of three challenges, and I absolutely promise the idea of using a corner stamp came to me before I'd scrolled far enough down the page to see DT Stef over at CAS Colours and Sketches had the same thought!
CAS Colours and Sketches - Challenge #121 Sketch
CASology - week 143 Ombre
Color Throwdown - #339 Black, White and Yellow