tiles

VersaTiles is a fully open-source stack for generating, distributing, and using map tiles from OpenStreetMap data, eliminating the need for combining multiple tools. Featuring a four-step, customizable process chain, it allows flexible integration of different tile sources, servers, and frontends.

LDtk (Level Designer Toolkit) is a modern and open-source 2D level editor, specifically designed for indie devs.

Tiled is a general purpose tile map editor. It's built to be easy to use, yet flexible enough to work with varying game engines, whether your game is an RPG, platformer or Breakout clone. Tiled is free software and written in C++, using the Qt application framework.