When assigning image/jpeg to the "file format:" pull-down for a wms layer and then displaying the layer the sites/all/modules/openlayers/OpenLayers-2.9.1/OpenLayers.js file changes the format from image/jpeg to image/png. I have temporarily fixed this by finding the 2 places where /OpenLayers.js changes image/jpeg to image/png by preventing this from happening. Somehow what is passed to /OpenLayers.js as far as the format is interpreted as needing to change from image/jpeg to image/png. When I use openlayers outside of Drupal and the openlayers module and pass a format of image/jpeg to openlayers it does not change it to image/png.
Below is the area that I had to modify within /OpenLayers.js: