You should just create a template - white rectangle with a smaller transparent rectangle. Drag it into a new layer, rotate it to where you want it, add a dropshadow, rinse and repeat. Because it is using layers, you can just erase out the frames that show through from underneath.
@bobfoto You do have to have your crops ready first...I've only done it once and wasn't too happy with it, but it did let me choose how much white framing I had.
http://www.youtube.com/watch?v=_evM0BAL3hE
Or try these -
http://rawimage.deviantart.com/art/Polaroid-GENERATOR-V1-42651542
I haven't used them.
created by david hockney ...
you can also generate your photo here:
http://bighugelabs.com/hockney.php
This is mine, I used Photoshop and followed this tutioral, http://www.youtube.com/watch?v=lJBskkf0UjA