i realy like this maniupulative image. It shows a teransformation the technique could be used in many different places and contexts.
Optische illusies maken met de kinderen
Quirky, Colorful Photos by Linus Lohoff
More cool effects with photoshop. I choose this not because it utilizes a ton of art principles but because it shows very basically how you can turn something so simple into something so fun. Could be a great magazine ad.