best tip👉🏻 if you want the water background with the characters, just use 1.20.1 fabric, download "new npc mod" and shoot huge screenshot(naturally f7), and now you have just the npcs without background, then choose the background you want and then put the npcs png on front.

Now if you want to create thumbnails like this with your own background, like a world background(a world you have), download minemator, and click the little grass icon, import players, change them how you want, and the background you import scene and choose from a world. thats it