Geoff:
In your gauges.js file, on line 20, is where you specify the location of your graph files, relative to your steel directory. Here is what your line 20 currently looks like:
imgPathURL : '/', //*** Change this to the relative path for your 'Trend' graph images
try editing this line to tell Steel Gauges to move up one level in the directory by inserting a period, so that it reads:
imgPathURL : './', //*** Change this to the relative path for your 'Trend' graph images