OK Mark perhaps the easiest way to do this
Attachment 93228
Is make your circle in XPG and copy then in X3D (any version) in the main window from the edit munu paste, then using the I-beam cursor with nothing selected press Enter one time and you should see a blank screen with the I-beam cursor still showing then paste again this will give you what I am showing in the text window above. Now select one circle with the I-beam and texture it, then turn off the I-beam then turn it on again (I don't know if this is necessary, but it is for me) select the other circle and texture it with your other image. Now when you animate you will have a two sided animation. This works best for me if I check the box (show the front face only).