There are two ways to pull a CSV file with all of your stock items depending on your needs:

1. Whether you have access to an FTP/SFTP or a Dropbox account, you can set up export in Settings > Export Data > Export type: Inventory Images

Full details on the specifics, selection criteria, available columns, and available filters are listed here. 

2. To download a CSV of your item images locally, you can use Dashboards > Query Data > Query type: Product Images.

Full details on the given Query Data report are available here.