I added a background in my scene init,as a sprite. I'm drawing my game elements as polygons: ccDrawPoly. But the background appears on top of my polys which are thus rendered invisible.
Is there a way to get around this and show my polygons over the background?

Put the draw calls in a node that has a z order higher than the background.

Or reverse the order you draw the polygons. Or disable GL_DEPTH_TEST (if its enabled).

I figured it out!
the background has to be added with z of -1.
I think the draw method has a z of 0 by default. (I couldn't figure out how to increase the z of the objects drawn with draw.)
thanks everyone

Yes, the draw method is effectively called with a z of 0 and you can't change it. You can trigger the drawing from a subnode if you need more control over draw order.