The ImageMap extension emits markup with typeof="mw:Extension/imagemap", not standard parsoid image markup. For this reason, the bundler does not include those images in the bundler (and the renderer does not render them, either). The GraphViz extension is also affected, since it uses ImageMap for its output.
Note that GraphViz emits markup with typeof="mw:Extension/graphviz" and typeof="mw:Extension/mscgen". So, even though GraphViz uses ImageMap for generating HTML output, making the OCG bundler and renderer recognize mw:Extension/imagemap won't help GraphViz.