The aesthetic design here is more about the Art Nouveau style of Club 33, especially after its big 2013-24 refurbishment. It's clearly trying to play up the New Orleans Square look and Art Nouveau style of the early 1900's, but then as Haunted Mansion is literally right next door to Club 33's expanded footprint and the windows in the bar look right out at the Mansion area, the coincidence in your mind is very understandable.
They really brought the Club 33 vibe forward in time a bit, from it's more obvious late Victorian or Edwardian era look it started with in the 1960's, to a look that is Art Nouveau on the cusp of becoming Art Moderne. (And frankly, the redecoration it got in the 1980's looks very dated and clunky now in comparison, and that's the look it still had when I first went to Club 33 in the 1990's). I'm no art historian, but that's what I get out of it anyway.
You can see the French Art Nouveau influences once you are allowed into the courtyard before you go up these stairs, with the statuary and handrailing and lighting that looks like a 1910's upgrade on an original 1850's New Orleans townhouse...
And then you arrive in this secondary upstairs lobby where we were checked-in for dinner and shown to the lounge for a bit, and this area is definitely Art Nouveau but also leaning towards the later Art Moderne period especially in the main chandelier in this space..
We'd probably need an Art Historian to clarify all that, as I may have my periods wrong there (Art Nouveau preceded Art Moderne, before it became Art Deco, right???), but that Christmas decoration was definitely designed to evoke the Club 33 vibe and aesthetics you experience in the main Disneyland facility in New Orleans Square. The 1901 vibe is decidedly more casual, and almost Bohemian in its aesthetic.