a) Vizard comes with a sample sky cubemap. You can use the following code to use it:
Code:
sky = viz.add(viz.ENVIRONMENT_MAP,'sky.jpg')
skybox = viz.add('skydome.dlc')
skybox.texture(sky)
There are many sample sky cubemaps available online as well. Just do a google search for them.
b) Light object do not cast shadows. If you need static shadows, then the best option is to bake the shadow into a lightmap using a tool like 3dsmax. If you need dynamic shadows, then search through the forum. There are a few sample scripts posted showing how to setup shadows in Vizard.