+-+-+-+-+
|?| | | |  first step: place a photo in the "?" cell
+-+-+-+-+
| | | | |  available photos: 2x2, 3x1, 1x1, 1x2, 2x1, 1x2, 1x1
+-+-+-+-+                    ***
| | | | |  
+-+-+-+-+  first photo that fits is the 2x2

+---+-+-+
|///|?| |  next step: place a photo in the "?" cell
|///+-+-+
|///| | |  available photos: 3x1, 1x1, 1x2, 2x1, 1x2, 1x1
+-+-+-+-+                         ***
| | | | |  
+-+-+-+-+  first photo that fits is the 1x1

+---+-+-+
|///|/|?|  next step: place a photo in the "?" cell
|///+-+-+
|///| | |  available photos: 3x1, 1x2, 2x1, 1x2, 1x1
+-+-+-+-+                         ***
| | | | |  
+-+-+-+-+  first photo that fits is the 1x2

+---+-+-+
|///|/|/|  next step: place a photo in the "?" cell
|///+-+/|
|///|?|/|  available photos: 3x1, 2x1, 1x2, 1x1
+-+-+-+-+                              ***
| | | | |  
+-+-+-+-+  first photo that fits is the 1x2

+---+-+-+
|///|/|/|  next step: place a photo in the "?" cell
|///+-+/|
|///|/|/|  available photos: 3x1, 2x1, 1x1
+-+-+/+-+                         ***
|?| |/| |  
+-+-+-+-+  first photo that fits is the 2x1

+---+-+-+
|///|/|/|  next step: place a photo in the "?" cell
|///+-+/|
|///|/|/|  available photos: 3x1, 1x1
+---+/+-+                         ***
|///|/|?|  
+---+-+-+  first photo that fits is the 1x1