We've just launched the ability to drag and drop files into any chat room.
During our Beta period, the file size is limited to 5MB. Once we've ironed out any teething issues, we'll look to increase that.
How it works
Quite simply, drag a file into any chat room, you'll notice a progress bar above the chat input area as the file uploads and processes. We'll make a thumbnail out of the file if we support it (images and PDFs for now) and once the file is processed it will appear in the chat area.