Based on Thierry's suggestion, this is what we would usually call it in the UK; or abbreviated to 'ID' The 'channel' could be dropped, but not the visual, since a 'channel ID' is something different — the kind of channel identification logo that comes up before programmes (which I'm assuming this is NOT!) I take it to mean the overall 'graphic imagery / presentation style of the channel' — the equivalent of 'corporate visual ID' in the business world.