If you thought that photos can only be altered professionally with software like Adobe Photoshop, you are mistaken. Even long before computers existed photos were altered for instanced to remove political party members who have fallen from grace or to create beautiful art.
Please check out the following websites displaying altered photos without the use of computers:
http://twistedsifter.com/2012/02/famously-doctored-photographs/
http://twistedsifter.com/2012/09/photo-manipulations-before-digital-age-photoshop/
http://www.mymodernmet.com/profiles/blogs/jerry-uelsmann-surreal-photography