The Tilemap Tool by iDev Games is designed to make tilemap asset creation easy and helps in creating asset store preview images for your asset store listings.
Load your tilemaps
The tilemap tool will allow you to load in your tilemap design in sizes 32px x 32px, 64px x 64px and 128px x 128px tiles. Then paint with your tilemap to see how it will look.
Currently only available on windows.