First I changed the source image to a "cloudy day" following this tutorial.
But as the flowers were too bright, I selected all but the sky, control+J.
I desaturated this layer and blend option to overlay.
Then I duplicate background layer and put it on top.
In image adjustments I changed contrast to +10 and saturation to +30. Now I have a sunny day too!
step 3 of 3
Then I made the puzzle as in the tutorial:
http://mi-hi5-activo.foroactivo.net/t185-tutirial-efecto-puzzle-en-photoshop-cs4
Sorry it's in spanish, but it's the one I used... I'm sure there must be the same in english tough!