In Excel 2007, you can use the "Selection Pane" to select and delete multiple pictures at once. Here's how:

1. Click on the "Home" tab in the ribbon.
2. Click on the "Find & Select" button in the "Editing" group.
3. Select "Selection Pane" from the dropdown menu.
4. The "Selection Pane" will appear on the right side of the screen.
5. In the "Selection Pane", you will see a list of all the objects in your spreadsheet, including pictures.
6. To select multiple pictures, hold down the "Ctrl" key on your keyboard and click on each picture you want to delete.
7. Once you have selected all the pictures you want to delete, press the "Delete" key on your keyboard.
8. The selected pictures will be deleted from your spreadsheet.