Regarding the eiffel tower:
Image rights / the Eiffel Tower brand
By day, the sun light and the eiffel tower are in public domain, you can take it in picture and publish / try to sell the pictures as you want.
By night, an image of the eiffel tower, if under artistic image-projection lighting, is under copyright if it's the main subject of the picture.
I think if it's for your little blog among your friends / a little audience, it should be ok (writing the "copyright Tour Eiffel - illuminations Pierre Bideau" is a plus).
If you have a big blog or try to make a commercial use, note that The Société d'exploitation de la tour Eiffel (SETE) states that the various illuminations of the tower are trademarked, and claims that they are under copyright, but this has been proved in a court only with respect to image-projection lighting, not the normal night-time lighting.
Regarding someone in a picture:
If someone makes a picture of me, who owns the right to it? - photo.SE
Personality rights - Wikipedia
If the person is the main subject and you can recognize them, you have to ask them before to publish.
If they are far away and barely recognizable it's ok.
(There is an exception for public figure during public life.)
