If you will be visiting Paris, don't forget to take some shots of the major Paris landmarks. Shots of Paris landmarks are selling very good, some of them are my best selling pictures.
Especially photos of Eiffel Tower are very popular:
Don't forget to go to the top of the Eiffel tower, there is a beautiful view of Paris
and you can also take a lot of "bird's eye" pictures of near landmarks:
Also Arc de Triumph and Notre Dame de Paris are selling very well, so don't forget to take some shots.