godot-module-template/engine/editor/icons/TileSelection.svg

<svg xmlns="http://www.w3.org/2000/svg" width="5" height="5"><g fill="none"><path stroke="#fff" d="M.5.5h4v4h-4z"/><path stroke="#000" d="M1.5 1.5h2v2h-2z"/></g></svg>