I can only come up with one for this one: perpendicular. But I don't think it is the right adjective.
Initially, I ask what is the sinuous wave in the picture appearing in the 404 page of Academia SE: What does the image in the “404 error” page mean?
The answer is the bike rack. But as the illustration shows, the bike is in the parallel position of the rack, not perpendicular as in the photo.