Hey there. Thanks for the post!
With images that are attached to posts using the attachment option (in the right column) by default you won’t see a preview of the image, just the file name and an icon. If you are adding the image into a text field to be embedded, it should use a local reference to the image and display it in the text field. If you’re not able to view the images when clicked as an attachment or when embedded into a text field there could be an issue with the attachments directory you’re using or user permissions for the TestRail user/system.
As a first step I would recommend double checking the attachments directory you’ve specified is fully writable to the IUSR user.
If you’re still having trouble, please reach out to our support team at firstname.lastname@example.org so we can get a little more information about your set up and our team will be happy to help further. Cheers!