R. Stannard shows how to use ELT Pics, which is hosted by Flickr. You can also get an email feed to show pictures as they are updated. A nice way to garner resources for writing or student projects. Pictures are crowd-sourced, and curated by EFL teachers. I use pictures often for teaching writing: description, emotions, cultural comparisons, if-clauses, etc. Don't miss the "Making Collages" part of this video, as it includes PicMonkey, which has templates for collages. ELT Pics also has its own blog with ideas for using images.
The blog for the Flickr group that collects pictures to use with EFL/ESL students. Join the crowd-sourcing, and use this blog to get ideas for teaching with pictures.