There are two ways to create a Tile Asset in Unity; the first method is to directly create a Tile Asset from the Assets menu. The second method is to automatically generate Tile Assets from a selection of Sprites.
Import the individual Tiles or Tileset images for your Tilemap into your Unity Project by placing the Textures into the Assets folder. Select the imported images to view their Texture Importer settings in the Inspector window.
Sprite Importer settings.
When importing Sprites for use in a Tilemap, use the following recommended settings. For further information about each setting, refer to the documentation on Texture Type: Sprite (2D and UI).
Tiles can be automatically generated by bringing the individual Sprites or Sprite sheets of the Tiles directly into the Tile Palette window (if the window is not open, go to Window > 2D > Tile Palette).
First prepare and import the Tile Sprites, then open the ‘New Palette’ drop-down menu in the Tile Palette window. Select an existing Tile Palette from the list, or select ‘Create New Palette’ to open the Create New Palette dialog box.
The New Palette drop-down menu.
After selecting the properties of the Tile Palette (refer to the Tile Palettes documentation for more information about the different options), select Create to open the new Palette in the window.
Select ‘Create’ to create a new Tile Palette.
After creating or loading a Palette, drag and drop Textures or Sprites from the Assets folder directly onto the Tile Palette window. You will be prompted for the save location for the new Tile Assets. Select the save location, and the new Tile Assets are generated in the selected folder. The generated Tiles are also automatically placed onto the Palette.
Tile Asset credit to Kenney
When you delete Tile Assets, they are replaced by placeholder Tiles made of a white square tinted with various shades of pink. The placeholder Tiles are placed on the Tilemaps in the original positions of the deleted Tile Assets.This helps to identify Tile Assets which have been deleted in a project, whether intentionally or accidentally.
Each deleted Tile Asset has a corresponding placeholder Tile with a unique shade of pink that differentiates the placeholders from each other. You can replace these placeholder Tiles with another Tile by using the Flood Fill tool or remove them.
Left: Tile Palette with three different colored Tile Assets (named after their respective colors - White, Red and Blue). Right: Tile Palette after deleting the the White and Blue Tile Assets. The Red Tile Asset has not been deleted.