TIP#262 proposes that frames should have an option for setting a background image. This Page was started so some graphical examples of frames with backround images could be displayed along with a discussion of the proposed change.
The TIP#262 can be found here http://tip.tcl.tk/262.html
After this was published, it became apparent that nested frames might present a problem. I think that having a -transparent option for frames might enhance this. Below is a screenshot of 2 sets of nested frames with buttons, where the upper set is how they would look without images and without the ability to set a frame transparent. The bottom half shows how this could look with a background image and a frame (enclosing the 3 buttons) that has been set to be transparent. Since this is not yet implemented, the below image is merely my photoshop'd version of what it might look like.
To implement this using the tip, (and an option -transparent not yet included in the tip) should be like so:
Frame11 configure -backgroundimage $apattern -tile 1 Frame8 configure -transparent 1
which would take an image, tile it (repeat it) as needed to fill the frame, and then make Frame8 transparent so the buttons appear to hover over the background.
Note: Frame11 and Frame8 are command aliases to frames. I use Visual Tcl for this which generates command aliases to each widget that can then be used to configure the widget.