Can any user help who uses Shareapic?

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Shareapic! The site you earn money on by sharing pictures. I have downloaded Wallpapers from wcremix.com on my computer. Am I allowed to share these pictures without copyright infringements? #1 I see these Wallpapers hosted in different locations other then wcremix.com i.e. http://photos.imageevent.com. #2 The wallpapers have the site name written on them. #3 I see other users on shareapic posting galleries of wallpapers. How can you meet copyright infringements? Is it when you post photos of maybe other people you know without there consent? Or is it when you take photos of maybe a particular site when they have the photos unable to be 'saved as'? Or is it when you go ahead and print them and try to sell them?