I had several managers ask if they could attach work products or reports showing performance...to a feedback loop. As a reference to what is in the loop write up. So attaching files, I think is a great idea. 

Perhaps to add to what Christina is saying...how about integrating with tools like sharepoint, huddle, box, asana, so those files can remain in the tools where people work, but can be referenced into loops and feedback in Rypple. So feedback be be contextual and reference actual work.