I'm interested how you are using an image map to link to a
tex box or positioned box. The idea of image maps is that the link
links to a topic. Also the fact that you are using text boxes AND
non-scrolling areas is I believe the problem. They are not designed
to work well together. Unless someone else can think of a solution,
you'll have to use one or the other.
If I read your post correctly, you are trying to overlay an
image on top of another image. And linking those to topics. No?
I think the best way to combine images is to do it with image
processing software and not try to have HTML code do it on the fly.
I would simply create a new image combining the images and then
create an image map to divide the active portions of the new image.