A couple days ago I mentioned the interesting use of flickr in Steve’s App Sketchbook email campaign. This morning I got this Halloween-ish email from ChoppingBlock that also used flickr in an interesting way: they invite you to post a high-res image from flickr to your blog, to see if you can name all the spooky characters in their latest tshirt:

Twitter and Facebook seem to be getting all the attention from email marketers now (see: Sharing with Twitter v. Facebook), but don’t forget flickr, because it can be a great way to get your subscribers to contribute to your conversation with photos!