The file name you would give to MediaLab would simply be continuum.htm as in the sample que file above. Note to modify the length of the slider you can just modify the code in the htm file to whatever percentage of the screen (or number of pixels) you like:

<table border="0" width="70%">

And to get rid of the value appearing at the right, change:

<input type="text" name="<ml.varname>"

to:

<input type="text" style="color:white" name="<ml.varname>"

As far as displaying images within the continuum.htm page, make sure you are using the angular brackets around the image name. If the image does not appear, replace <ml.background> with the name of a specific image in the same location to see if it appears properly. If so, attach a zipped copy of the html file and image file and I'll take a look.