Considering there isn't a screen in Rally to see all attachments across our entire subscription:
Is there a way to get all information of all attachments in our subscription?
You can use the Excel add-in to export the details of all attachments including their Names, Descriptions, Artifacts, Creation Dates, Users who added them to your subscription etc..
Here is how it works. In this example we will defined a query named: "AllAttachments" and select some of the available fields to export to our spreadsheet: