If you're trying to find out which images in your email are not referenced from the sending account, you can look at the image references in the HTML code. The URL will either contain a reference for images hosted on your site or from your VerticalResponse image Library.
For images hosted on your site, you can check the URL by opening the image in a new browser window.
Images coming from a VR account the link will look like this:
The "651f8g9a86" in this URL is the identifier for which account the image "belongs to." To check if you're using the right identifier, check your account's image Library and check out the URL of the images.
To get to the library, click Tools>Library, then click on the title of the image. You'll see your account's identifier there.
If all images in your email don't match this identifier, you can replace the images in your email. An easy way to to replace the images is to upload your images to your account library to create the correct URLs, and then import them into your email from the library.