[Update]: There have been important changes to how Google Drive handles direct links. See what’s this all about.

You might wonder how direct image links or direct URLs are related to email signatures. If you can use an embedded image, you do not have to worry about any links. However, linked images have some upsides: for example, they don’t increase the email size. What is more, there are situations in which linked images are the only available option. To add a linked image, you need a direct URL to it.