- Are any of these made by hand using pixel art? There seems to be something very hand painted about all of them.
Definitely not pixel art, but clean airbrush/more common digital art.
- IF these are hand painted, does anyone know how something like that would be incorporated into a game? Would it just be one very large image/PNG? Or would there be a ton of layered images that get pieced together?
Depends on how the rendering engine is put together. Just using a large PNG would be the easiest, but nothing would be re-usable, and you'd probably need some sort of back-buffer for collision detection and such (for example, using an image the size of the foreground that has colors like white representing walkable space, black meaning non-walkable space, blue being a path of lava, etc. -- at least, that's a very easy way.)
- Are there advantages/disadvantages to using Pixelart VS/OR Digital painting for backgrounds?
Pixel art uses minimal color counts; it also can therefore be compressed better when size is an issue. For an aesthetic point of view, it gives a clean and somewhat-retro look. It really depends on the game/project, and even more so on the intended aura the game creates, which is chiefly determined by the style of the graphics, the detail level of the graphics, the arrangement of the environments, the characters in the game, the storyline and setting, and how the music works with all of them.
- How would one go about pixeling an entire background for a game. Would you do it with individual tilesets or create one very large pixel background?
Depends on how the rendering engine is written and what the artist is willing to do.