1) Log into your DotFeed portal at www.aspdotnetstorefront.com/license/DotFeed.aspx
2) Find the feed from your storefront to Google. On the right, click MANAGE and choose Configuration.
3) Click "Edit Configuration". This will enable the editable fields.
4) Now save (this is to implement the feature for image management).
5) You will notice that you now have a new configuration item, "Image Size".
6) Once more, choose "Edit Configuration" and drop down the "Image Size" - change this to any of small/medium/large, to suit your own needs.
This is useful for any users of AspDotNetStorefront who find that the wrong images (or no images at all) are being fed to Google. This is most frequently caused by modified display pages in the storefront.