One I retweeted earlier, from the amazing 500px.com (on Twitter as @500px):
— 500px (@500px) October 3, 2014
I never use Google Images to look for images to use in class, but see so many great images by following people like 500px on Twitter. If you "favourite" them on Twitter, you don't need to bother downloading them and can access them big! If you then display them with a projector rather than with an A4 photocopy, you'll get people to say so much more — because they can see it better.
THAT'S the kind of pic u want for #ELT class: huge, online, strong character, multiple imaginable stories
— Tom Walton (@Tom_IHBCN) October 4, 2014
Both for speaking and for writing activities, you want images that suggest multiple questions to the observer, images that suggest multiple possible, imaginable stories.
That's the kind of image that is worth 1,000 words — because it will then get your learners to actually say those thousands of words.