Cannot Specify the imageURL for the SimplePreloader in 2.15.0-pre2

I cannot get the SimplePreloader class to use a user-specified image in place of the gear image in 2.15.0-pre2.

In past builds of Verge3D, I was able to have the SimplePreloader class use my own image in place of the gear by passing its constructor a value for imageURL in its arguments. This was an easy way of putting a logo of my own choosing on a loading screen. This was done like this:

    var preloader = initOptions.useCustomPreloader 
            ? createCustomPreloader(initOptions.preloaderProgressCb, 
            initOptions.preloaderEndCb) 
            : new v3d.SimplePreloader({ container: 'container' , imageURL:'my_logo_animated.gif', imageRotationSpeed: 90});

The preloader in 2.15.0-pre2 seems to ignore the imageURL property. Is this a bug? If not, is there a simple way to replace the spinning gear?
Thank you.