Are you using the correct yaw/pitch offsets that were specified in the user manual for your particular HMD model? These offset values can vary between different models.
Here is some code that will fill the entire window with a texture:
Code:
import viz
viz.go()
quad = viz.addTexQuad(parent=viz.ORTHO)
quad.alignment(viz.TEXT_LEFT_BOTTOM)
viz.link(viz.WindowSize,quad,mask=viz.LINK_SCALE)
texture = viz.add('image.jpg')
quad.texture(texture)