Hello, 

after following the instructions postet on the UI Customisation page specifically Replacing the Background Image via Setting I was not able to get any results.

I copied a link from one of the suggested pictures on the same page (Copied Image Address) and pasted it into the field Custom Background Image URL.

I also changed the value in the field Background Color as suggested to "242 242 242 0"

Phone and Firmware: snomD385-SIP 10.1.57.14