S1MD Green Hill Zone tilesets in S1MDMS style by HidroGeniuns on DeviantArt

Sonic Mania - The Cutting Room Floor

Mighty in Sonic 1 Rev 1.1 with Knuckles Chaotix sprites (S1 Hack

Sonic the Hedgehog Sprite Sheet - Evil Sonics Sonic Hacks

The Leaf Forest Zone - Sonic Advance backgrounds

I made Green Hill Zone in note blocks for my friend's Minecraft recreation of Sonic The Hedgehog (1991) : r/SonicTheHedgehog

Mania Madness Ep. 1 Preview Green Hill Zone W.I.P. (Sprite Animation)

The VG Resource - Dolphman's sprite library of customs & edits

Sonic The Hedgeblog — Past Green Hill 'Tails & The Music Maker' SEGA

Secrets of Sonic the Hedgehog

Sonic Platformer Game