PIC1.PNG can be transparent and that's awesome!
The background image used by applications and games is the PNG file format. So i got the crazy idea, what would happen if i made one with transparency?
Well this is the result:
Really really sexy stuff comes by out, you get the xmb wave and the sparkling in the background, awesome! I have never seen that effect on an retail game before.
You could go there and make some vector style artwork with solid none transparent and transparent areas. Lot's of ideas! But that is upon you ;)
Anyway, in conclusion, there lies a lot of potential for creativity, and in my opinion this is a good way to separate Homebrew from Retail (since retail stuff doesn't use this effect).