This is an intentional Change currently, to combat ip sniffing attacks via images hosted on compromised hosters. Currently, ONLY ts3image:// URLs are allowed. So you would have to upload the image to the server and change the url (click share and adjust the scheme to ts3image)
This is a somewhat temporary solution - we are planning to rework this feature with sich safety issues in mind. Until then, use the File Browser for images (S3 and non-S3 work)
As a suggestion, it might be worth adding a client side option (defaulting to true) to block external image links. This way, users could consciously decide whether to take the risk.
Either way, I greatly appreciate your quick response have a nice day!
Upload image to display in any channel on your server
Right Click that Image in the File Browser → Copy URL
Go to your Channel Description and Edit it
Paste your URL and wrap it in [img][/img] (e.g. [img]ts3file://my-server?port=9987&serverUID=<some-long-uuid>&channel=1&path=/&filename=banner1.png&....[/img])
replace ts3file:// with ts3image:// at the beginning of the URL (e.g. [img]ts3image://my-server?port=9987&serverUID=<some-long-uuid>&channel=1&path=/&filename=banner1.png&....[/img])
You can even delete nearly all parameters of that URL except channel and path and move the filename to the front: e.g. [img]ts3image://banner1.png?channel=1&path=/[/img]