Right now we've got the "Recent Forums Images (Attachments)" plugin installed and my members really like it. They have suggested that a new type of stream that showed that content would be a great addition to streams. It would give an instagram-esque listing of all the recently-attached images matching the stream criteria. 

Would be cool idea, probabaly a plugin request though rather then part of the core. But either way I would be interested. 

I wasn't sure how "pluggable" streams were, considering that they are brand new.