The original Game Boy (DMG/CGB/etc) is limited to 8x8 and 8x16 sprites, or a larger meta-sprite composed from up to 40 of those smaller, individually managed sprites. There are some workarounds, but generally this limits the maximum size of sprites to a small size on an already small screen.
As an exercise, this demos using the video overlay Window as a huge pseudo-sprite (with some limitations). The priority feature and transparent pixels of regular sprites are used to create some foreground/background layering.
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Star sprites: S_PRIORITY flag set so they appear behind the Window sprite, except where it's pixels are set to color zero.
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Game Boy sprites: S_PRIORITY flag not set so it's above the Window sprite.
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Background layer: All pixels set to color zero.
Built with GBDK-2020 - https://github.com/gbdk-2020/gbdk-2020