adding attachment to Excel template

Hello All,
I'm in the process of creating a template where my audience can create user stories. In "Attachments" section of the attached, I would like for my audience to be add to choose a file and add it as an attachment to the template.
This would most likely be picture of a mock up or an excel file. It would be cool if the user added an excel file to the template then the little excel file picture was populate.

All help is much appreciated!

Cheers!
Andrew