You'll need 4 pictures. Open up your main image. Make it fairly large, the size of your desktop. Next take your other 3 pictures and paste them on to a 377 X 298 px. document. Make a nice blend and then merge your images together and paste them to the main picture. With the blend layer still selected, copy the layer (ctl + J) and go to Filter Render pixelate Cell Size 8. Resize the un-pixelated picture so it's smaller than the pixelated one. Rotate your blends on an angle and you're done!
Oops!
Oops, you forgot something.