Try searching Flickr.com Morguefile.com freefoto.com and bigfoto.com and deviantart.com. You can usually have posters printed and shipped to you from most of those places.
Here's some stuff I found on deviant art, I'm pretty sure you can buy posters from the artists:
http://www.deviantart.com/deviation/...+age_scale%3A5
http://www.deviantart.com/deviation/...+age_scale%3A5
http://www.deviantart.com/deviation/...+age_scale%3A5
http://www.deviantart.com/deviation/...+age_scale%3A5
http://www.deviantart.com/deviation/...+age_scale%3A5
http://www.deviantart.com/deviation/...+age_scale%3A5
http://www.deviantart.com/deviation/...+age_scale%3A5
http://www.deviantart.com/deviation/...+age_scale%3A5