Hey Zoe, I'm going to give this a shot...........
Open the image you wish to create the
cascading photo collage effect on.
On a new layer, use your
Pen Tool to create a perspective line for your
cascading photo collage to follow. Your going to turn this off when done.
On a new layer, use your
Pen Tool to create a photo outline that has perspective. When done, right click and choose make a selection.
Fill this selection with white.
With the selection still active, go to SELECT > MODIFY > REDUCE, enter 12 pixels, hit OK.
note:
Remember that the reduction will get smaller in perspective, so the next time you do this enter 10 pixels.
Create a new layer and fill the reduced selection with black.
Now we have to add a image to our faux photo we just created.
Open the image (beach) you would like to go in this faux photo.
Place it above the black layer we just created.
Hit
Command + T to enter
free transform, right click and choose
distort.
Dragging with your mouse, place the corners of the image (beach) to match the faux photo. Hit OK or enter to accept the state change.
note:
You could also use Warp to generate a curve in the image (beach) to match the curve of the faux photo.
Now clip the photo to the black layer. and your done.....with this one!
Now do the same thing for the rest!
If you make it this far, I will demonstrate how to add shading, shadows and motion blur!