Linux: image viewer with transparent window?

Solution 1:

To my knowledge, window transparency is the job of the window manager. I'm pretty sure--but someone please correct me if I'm wrong--that the only way to accomplish this is by using a window manager, such as Compiz, that supports transparency.

How come you don't want to use Compiz? If you're just trying to avoid Gnome and KDE, you can use Compiz independently of your desktop environment.

Solution 2:

I use transset, you can make any window whatever level of opacity you want. Since it is command line you can write scripts that call it.

example:

transset -n "Window Title" 0.5