CubeTextures are in groups of six for each side of the cube, each starting with a common name.
They look like below when grouped, but actually there are 6 images in common folder
See also Skyboxes | Babylon.js Documentation
Your file seems to be just one plain image. If you want to use one file for the environment - use ddr. or env files for this: Using An HDR Environment For PBR | Babylon.js Documentation
Ok,what if I just set a background image for the scene?
In this case you may use Layer for the background - https://www.babylonjs-playground.com/#IH5G0H#15
Or make the canvas transparent with
scene.clearColor = new BABYLON.Color4(0,0,0,0)
and use usual CSS background like here - 1001 Minutes - BabylonPress
Thank you for your reply, your methods resolve my question, thank you very much