**Regarding the eiffel tower:**  
[Image rights / the Eiffel Tower brand][1]  
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, the eiffel tower artistic 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, you must ask (and pay) for the right at the Eiffel Tower company (SETE).

**Regarding someone in a picture:**  
[If someone makes a picture of me, who owns the right to it? - photo.SE][2]  
[Personality rights - Wikipedia][3]  
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.)  


  [1]: http://www.tour-eiffel.fr/en/the-eiffel-tower-image-and-brand/image-rights-the-eiffel-tower-brand.html
  [2]: http://photo.stackexchange.com/questions/25511/if-someone-makes-a-picture-of-me-who-owns-the-right-to-it
  [3]: http://en.wikipedia.org/wiki/Personality_rights