For graphics such as the FrameAbove and FrameBelow horizontal lines used around some FrameMaker formats, you might get better results by replacing the reference-page graphics with HTML horizontal rules. This approach avoids carrying an extra generated .jpg around for every FrameMaker file you convert. For example:
Note = CodeBefore CodeAfter NoFrameAbove NoFrameBelow
You can tune the <hr> rules by specifying width, height, or other attributes, and possibly by using a class to apply CSS properties; see §22.7.2 Mapping paragraph formats to CSS classes.