body: I am designing a poster for my school competition but I am concern about the legality regarding the usage of online pictures. Most of them are under CC BY-NC-SA 3.0 and I know what each term roughly means. 
  
  
  However I am still very new to all these and will like to confirm that using them for my poster design competition is considered sharing and not commercial.
  
  
  In addition, under attribution (BY), do I need to give credit to the pictures on my poster? I think it will look really unglamorous to include the source for each of these pictures on my poster and wondering whether I can get away legally without including them.
  
  
  
title: What kinds of pictures can I used for my poster without violating copyright laws?