components of my mitered frame action:
I used wood veneer samples from the internet to create a vertical and a horizontal pattern. To make the pattern seamless, use the offset filter and clone noticeable transition areas.
The action creates a duplicate image so that the original won't accidentally be overwritten.
After the action has run, all layers are editable. In this case I added color and texture to the background "wall".
The bevel "cut" in the matte is part of the top image layer. This way, the image can be repositioned and the bevel cut will follow.
Matte size and wall size are editable while the action runs. The basic frame thickness is dependent upon the starting image size. The action works best in the range of 600-1000 pixel dimension. If the image is too small, there is an error and the action quits.
The mitered corners are created by using different pattern images for the horizontal and vertical sides.

forum discussion http://forums.dpreview.com/forums/read.asp?forum=1006&message=26587604