Creating 2D tileset for a platformer is a real breeze. I can imagine it can be used for creating top-down tilesets too.
There are basically two ways of creating the tiles. First, you prepare the tiles beforehand, upload them to AutoTileGen and just let it do its magic. The tool gives you some tools to tweak the borders, corner blends and overlaps, then save the tileset in a PNG. Second, you can use the built-in pixel editor to create the tiles in AutoTileGen. Both approaches can be combined.
AutoTileGen is work in progress. There still are a few bugs and the interface lacks some useful options, but I am sure Javi is working hard to make the product perfect. If you are interested, check its crowdfunding campaign. It is near its end and there are plenty of stretch goals! People who back the project with $20 (which is the standard price of the Pro edition) will also get a free AutoTileSet plugin (think Tiled editor inside Unity and maybe other Game Makers soon) and PixelPerfect plugin which makes pixel art games in Unity look more "pixel" :)
Check the video to get better idea on what AutoTileGen can do. The video shows the Unity plugin as well.
And here's what I was able to do with zero knowledge of making pixel art and limited tileset experience in AutoTileGen. First a screenshot of my workspace when trying to make abandoned castle interior:
And the result, 16x16 complete tileset generated from AutoTileGen Pro. It is enlarged, because the original is too small.
Flappy Bird clone anyone?
SummaryAutoTileGen is really great for creating tilesets. The community of users is not big yet and the crowdfunding is still on. It's the best time to evaluate the tool and maybe suggest some features. AutoTileGen comes in Free and Pro versions, but the Free on is really limited and Pro totally worth the $20. Pro version features built-in pixel editor, normal map generation and preview and custom corner masks and more. In combination with the Unity plugin, AutoTileGen significantly shortens the time to develop let's say a 2D platformer and makes it possible to the artistically impaired devs (like me) to make some cool art!