I work for BYUtv and one of the most creative logos I've seen in a while is this one that KBYU 11 does. Our minds can make sense of the logo in two different ways, one seeing the outline of Utah even though it is not all connected and there is also an eleven. The eleven is formed by only using a single one but the other is easily distinguishable by the outline made in the other half of Utah. This both illustrate the principle of closure. 

The two elements in my smiley face design are proximity and similarity, the faces are very close together and can be grouped in a few different ways depending on the viewer, color, vertically, horizontally, transparency and many other ways. They are all also very similar but no tow are exactly the same, this also allows the viewer to group them easily