http://www.fmi.uni-passau.de/hilfe/inlined-images.html (Einblicke ins Internet, 10/1995)
NCSA Mosaic Inlined Images
Inlined Images for NCSA Mosaic
Introduction
NCSA Mosaic version 0.10 (and later) supports inlined
bitmaps and images in X bitmap and GIF formats. For example, here is
a bitmap: 
. Here is a bitmap serving as an anchor
to another document: . (If you were unable to see those bitmaps,
you're not using NCSA Mosaic version 0.10 or later -- shame on you!)
Dan Quayle
These bitmaps can be rather large; for example, here's Dan Quayle:
How It Works
To embed a bitmap or image in a HTML document, use the IMG tag. For
example:
<![CDATA[
<img src="[unarchived-media]">
]]>
To use a bitmap or image as an anchor, do something like this:
<![CDATA[
<a href="http://web.archive.org/web/199510/http://foobar.com/blagh.html">
<img src="[unarchived-media]">
</a>
]]>
This causes the GIF image named foobar.gif to be used as an anchor to
the document named blagh.html. When a bitmap or an image serves as an
anchor, it is surrounded by a colored rectangle and made sensitive to
mouse clicks, just like ordinary text anchors.
Note that the value of a SRC argument is a Universal
Resource Locator --- image data can thus lie anywhere on the
network; it is retrieved as the document is being formatted by Mosaic.
Once image data has been retrieved once, it is cached in memory, so
subsequent uses of the same image will be generally very quick.
For example, . Using this bitmap (which was also
used above) twice in the same document incurred very little additional
overhead.
Another Demo
OK, now that you sat through that, here's another demo, this time with color GIF
images.
Acknowledgements
The GIF-reading code NCSA Mosaic uses was written by Patrick J.
Naughton; his copyright statement is here.