According to the team of researchers behind the British TV show Quite Interesting (QI), “if you want to use a photo of the Eiffel Tower for commercial purposes, you need permission if it was taken at night but not if it was taken in the day. The copyright on the tower and its image has expired, but the copyright on the tower illumination installed in 1989 has not”.

I then discovered this fascinating blogpost over at Discvr.blog, all about the rejected designs for the Eiffel Tower.