Doxygen does have support for showing images, and there are
at least a few areas in BRL-CAD where this is desirable, but
the trick from our standpoint is twofold - first, the build
system will have to be taught how to place the images properly
as part of the dox build.  Second, where should the images
themselves live?  In with the headers and source code seems
clumsy... Perhaps a special purpose setup in the doc directory?

Until a decision is made, put images intended for doxygen use
here so they can be integrated properly once an approach is
decided on.

Ideally these would actually be generated by the build itself
wherever possible, but that won't be possible in all cases and
will be very difficult/complex in at least some others, so we
can't assume one or the other method as a general solution.
