When I was attempting to build a quest through the classic tileset, I had noticed a deficiency of dungeon wall tiles. Being bored with nothing else to do, I decided to make 1 square thick GB style walls. Once I had finished the walls, I decided to also make new block tiles, new floor tiles, and new water tiles. All of these tiles are hand-drawn and original sans for the statue that I based off of the LTTP snake one. I included two types of doors: Classic Style and Gameboy Style. Gameboy Style is easier to use, but Classic Style has the option of animated doors (that are a pain to set up and get functioning). The water and floor tiles share the same texture, but the water tiles animate in groups of two and are darker/bluer/redder (depending on CSet and palette) than the floor tiles. Another floor tile exists that I use for block puzzles, but they can be used for whatever. The lone lines are used for layering to make the Classic-Style doors have tops. Since these tiles use the original palettes, they rip into the classic tileset flawlessly.

Myself.
Nintendo, for making the original snake-statue in LTTP.