last issue first, the picture.
To make an html file portable you need to use a relative url, not an absolute.
as an example, take any webpage in your browser (the google.com homepage is good because it is simple)
and do a file->save as--> google.html
and be sure to use the Webpage Complete format.
if the page is saved in My Documents\google.html
there will be a new folder My Documents\goolge_files\
where all the graphics are stored
edit goolg.html and you will see relatice urls for files in google_files\
a relative url does not begin with http : // but (in the case above) "google_files/..."
SO; create your page
create a directory
place your graphics in the directory
reference them best with url = "./directoryName/..."
when you export to the USB, place the HTML in the partent directory of the directoryName