As The Flickr Collection by Getty Images has hit over 60,000 images, the site has announced a "formal Call for Artists".

This means that any of the 40 million-plus Flickr members can submit their work to be considered for the collection through the Call for Artists group on Flickr, rather than wait to have their image spotted by the Flickr team.
There's detailed guidelines over on the group page, but basically all Flickr users can now submit 10 images "that represent what you consider to be the best of your work".

The Getty Images creative team will then evaluate submissions based on style, subject matter and technical skill and let sucessful members know if their images will get into the group for possible licensing.