The odd shape of it suggests it was done manually. But the 'mosaic' effect may have been done using a special program. However, the effect can be done reasonably well with a native PS filter -- "Mosaic".
Here's some things to play with...
1)
Open a photo.
Double-click it to rename it, click OK.
Add a layer mask.
Add a new layer, drag it below the photo and fill it with white.
Back to the layer mask.
Paint with black over an area of the photo. Don't paint over all of it, and paint in the shape that you want the final image to display in. Keep the paint away from the edges of the photo.
Gaussian blur the mask by a lot... say 20 pixels.
Press Ctrl+I to Invert the colours on your layer mask.
Now run the FILTER/Pixelate/Mosaic filter. Set the size to whatever you like. Turn the "Preview" option on and watch your image as you adjust the size setting. Apply the filter when you're ready.
Voila! 
(see image below)
2)
With that same photo open, turn off the layer mask by holding SHIFT and clicking on it.
Add a new layer.
Run the Clouds filter, then Auto Levels.
Apply the 'Mosaic' filter to this clouds layer.
Set the layer to Soflight; but try Overlay/Hardlight/Vivid Light/Linear Light also to see what they look like.
Create a medium sized square selection (40pixels). On the photo's layer mask, move this selection around the outside egdes of the photo and fill it with black. Use Lee's sample image as reference to how random looking this outer edge pattern is.
Do this until you only have only a specific area of the photo showing.
(see the example in my next post)
:B TIP: You can change the look of the effects by running the LEVELS filter on the layer mask and the clouds layer. Just move the sliders around and you'll see how that effect the image (mask).
