The "Attachment Preview" section for an individual issue appears to only support previewing files if the extension is all lower-case.
Steps to reproduce:
1. Create a new issue.
2. Attach two valid JPG images, named lowercase.jpg, and uppercase.JPG.
3. View the issue in Visual Studio.
4. lowercase.jpg will be previewed, but uppercase.JPG will display the message "Unable to view attachment due to unsupported attachment type"