Gray background behind app windows?

Folks,

Apps like Photoshop (PS) used to have an option to blank out the  
desktop behind their windows to a flat gray. That reduced visual  
clutter so artists could focus on the app's windows.

I have Photoshop CS3, not CS4 (I tend to update every other time to  
try to save a little money) so I don't know how it works in CS4, but  
in CS3 under Leopard, it looks like PS turns the document window into  
a "super window" that fills the whole screen and has gray borders all  
the way around.

Our company is working on rewriting a legacy OS 7/8/9/ app for OS X  
(>= 10.5), and the legacy app has the option to blank out everything  
behind the app's windows to dull gray.

Does anybody know a way to do this in OS X without either going to  
full-screen mode (and losing Cocoa's support for document windows,  
tool palettes, etc.) or turning the front  document into a monster  
that takes up the whole screen, with the content placed in a  
resizeable view in the middle? That's doable, but less elegant than  
the gray background old OS 9 apps used to use, and doesn't allow the  
user to see more than one document window at a time.


Thanks in advance,

Duncan C
WareTo LLC