I like this pin because it's a very serious portrait, but someone added graphics that seem fun and playful when they move; the opposite of the portraits tone. I think they go nicely together without overpowering both moods.
"Vertical Landscape" by Eiko Ojala. It looks like a paper landscape but the artist actually works digitally and hand-draws all the elements to look like they're cut out of people. (Hint: the shadows help!
How To : Adobe Illustrator Geometric Art. This is a very interesting type of art. I do like how it uses simple shapes to create a portrait. I know for a fact that you can do this easily in Photoshop with one of the brush tools.