Tim,
Unfortunately, HTML does not include images.
A suggestion would be to create a GIF image, or to put everything in a zip file, or something to that effect.
I had to work with HTML documentation for LabVIEW, and actually used LabVIEW to substitute the images for control types with words, such that images were not required. You can try this if your images are nothing more than representations for which text can be substituted.
Alternatively, if your image is something like a graph, or the front panel, I might suggest creating a .gif or .jpg image out of it. This has to be done manually, but will make the page one single file.
Good luck, I hope that helps.