Yes the expense receipts associated with an expense sheet can be viewed without opening the expense sheet.
Click on the Expense icon in the top menu.
In the expense sheets for 'user name', you can see the list of open expense sheets.
To view the receipts of the any of the listed expense sheets, click on "Receipt List" under 'Expense Receipts' section.
In the 'Expense receipts' pop up box you can click on the "View image icon" below the 'View' section.