Sounds good!
I’d say:
Default for users: Keep the current default.
Default for additional filetypes for staff users: None.
In addition, I’d completely exempt admins from the check.
This means that…
- The defaults don’t change for non-admins.
- Admins can upload anything (which they already could do anyway, but with less comfort).
- If you want to allow moderators to upload additional file types, you can use the second setting for that.
- If you want to restrict image upload to staff only, you can remove all filetypes from the user-setting and add image files to the staff-only setting.