Darren…
Is my desktop Pictured here <
http://home.comcast.net/~phoz/ScreenCap.jpg>, something similar to what you’re talking about?
That picture of Escher’s "Drawing Hands" could be anything, of course. My main desktop color is the gray you see; the "Drawing Hands" portions are just a PICT file with a trnasparent BG, so that the gray shows through. If I change the main desktop color, it just looks like the drawing is on a different colored BG.
Just like on a PC, I could’ve also used a full, screen-size image of the "Drawing Hands" already embedded on it’s own colored BG. I like being able o change the color if I want to….though I don’t very often.
With Photoshop open, and all the palettes visible, this desktop background will appear behind the palletes and around any document window I might have open. I think, because you’re used to the Windows GUI, which, by default, opens windows at full screen size, you wouldn’t normally see the desktop. That "embedded company logo" you’ve seen is probably just a Mac desktop image.