The Ringworld is composed of a mythical substance called scrith. Niven describes scrith as being grayish and slightly translucent. For scenes like the above, where you see both sides of the ring, I check the normal and shade the bare scrith underside with a simple matte texture in a grayish color. The translucence of scrith is not apparent at this scale.
I used this and similar views to try getting a picture of the rim wall. Unfortunately, the rim wall is so small compared to the width of the ring that unless I shaded it in some garish manner, such as making it hot pink, it simply didn't show up at all.