Backgrounds & Photoshop Fun

I am learning so much lately... I especially love what I've been learning about Photoshop. I have CS5.5. The masking tool in this version of Photoshop is amazing. Rather than me trying to explain it, here is a link to a video that explains it quite well.
http://www.youtube.com/watch?v=iUUFIdAsj2o

So here's what I've done. I have a lovely picture of Abby on a plain blue wall and a macro photo of a rock I took at the Smithsonia Museum of Natural History.

Duplicate the Abby photo layer (Ctrl J). I brought the rock photo layer into the Abby photo and placed it below the Abby duplicate layer. Then I masked out the background of the Abby photo which revealed the rock photo below.

I did do several other adjustments to the Abby photo including removing a few blemishes, whiting the whites of her eyes, and altering the color of her irises to go with the color of the rock.

I played with this a little more with a great photo I had of Levi and a macro photo of Citrine. This time I changed the color of the rock photo (using a Hue/Saturation layer over the rock photo) to go with Levi's eyes.