"I have a script which needs to output both html and graphics on the same page. "
and
"..., it appears I will need to send two content-type headers ( text/html and image/png )."

The question was kinda tricky. My response did include the two request solution.

I doubt Cines answer below actually works on web browsers. MIME types and HTTP content-types are similar but not exactly the same.

Greetz
Beatnik
... Quidquid perl dictum sit, altum viditur.