You can annotate images received in the conversations you are participating in Slack.
How does this work? Well, after an image its posted to a channel, you will receive a message from our bot saying something like this:
After clicking on that link, you should be able to scribble your notes in the image and then post it right back to Slack. Easy, huh?
If you want to annotate all the way, you need to enable this feature in your settings page.
We have a few more things we plan to launch.