Fully transparent backgrounds??

[Atownbt]

Can you make a portion of the presentation layout be transparent so you can see the desktop (icons, wallpaper, everything) behind it? like the background image or color?

[acknak]

No, the document background is always filled with some opaque color.

Why do you need to see the desktop?

One possible workaround: you can show the presentation in a window--that can be moved or minimized like any other window. Unfortunately, you can't switch back & forth between full-screen and window modes (that I know of anyway).

[Atownbt]

Its so we can layer worship words onto live streaming video and feed it onto projectors without having to do a chroma-key setup.

[acknak]

I'm not sure that would work even if Impress could have a transparent background. It calls for compositing the contents of two windows, one of which is a video stream. That's still a pretty advanced feature--as I understand it anyway.

I guess this is obvious, but have you tried just making the video feed the slide background? My guess is that neither PPT nor Impress will be able to composite anything on top of the video.