hmmmm
if you want the cell-shaded look..
id suggest dropping all texture, and just outline ing whatever you want.
made another example, not entirely sure its what you are looking for though.
The base tile is just a solid colour (should be easy to tile
)
however, since it is just a plain tile, you are going to need to create other tiles to compliment it now.
I created 2 tiles with grass blades on them.
They might seem abit random with positing... but with one tile i had the large clumps on either side of the tile, then little bit on the top and bottom, as well as only 2 of the diagonals.
The other tile i have the large clumps on the top and bottom, and then just alittle bit on either side, and the opposite 2 diagonals.
This helps so that when you tile, all areas are covered once you start putting your tiles together, instead of leaving large open areas.
Somewhat helps to hide the grid too, since your spreading out grass blades over the edges (where the large clumps arnt, you are creating blades when you put the edges together).
I didnt use any highlights, since i was only outline ing the grass, rather than colouring it.
i also through in a possible idea of a bush.
With this style though you cant rely solely on the pattern of the grass, because, well there really isnt a pattern. So for this, you have to create more varied tiles such as bushes, or flowers, or other types of grass blades. Dont fill the whole tile, just add an accent to change it up.
perhaps maby that helps??
a good source you should check is,
www.dofus.com