No, you can't use the images stored in the library for other purposes or in other services. It is a private URL and can be used only within Zoho Campaigns.
The Images tab under Library module allows you to upload or import images and store them for future use. How do I upload images to the Library? You can upload an image either from your computer or from a web URL. Zoho Campaigns only supports images ...
If the images in the campaigns you send are blocked, your contacts can click the "Display external images" option when they open the email. To prevent this from happening again, they can select the "Always display images from this sender" option.