I've included a modified version of the skybox plugin that should work for cards without cubemap support. Place the contents of the zip file into the same directory as your script, or replace the existing plugin in the [Vizard25]\plug-ins directory.
To create a non-cubemapped skybox use the following example code:
Code:
sky = viz.add('skydome.dlc',1,'maps/sky.jpg')
You don't need to add an environment map. Let me know if this works.