This plugin allows you to create nicely textured 2D polys. Simply place a few points then create / assign the shape material, and you should have a good-looking polygon.

The textures used are similar to what you would use if making terrain using TileMap/TileSet

See Homepage here: https://github.com/SirRamEsq/SmartShape2D

Using SmartShape2D with Godot 4: https://github.com/SirRamEsq/SmartShape2D/blob/master/addons/rmsmartshape/documentation/Godot4.md

SmartShape2D + Aseprite tutorial can be found here (Thanks Picster!): https://www.youtube.com/watch?v=r-pd2yuNPvA