I'm inclined to say that the visual distance in game is 17x13 (8 squares left and right, 1 down the center, and 6 up and down, 1 through the middle) Or at least, last I checked it was. Or maybe that was after I added 1 to each end :O . That's probably cause my game has 0 fade screens from map to map and is rediculously fluid lol. Also makes mapping 10x more a bitch
haha.
Also, yes, Leventhan's mapping up there is prime. It's what you should be going for. Say that map was 20 blocks larger, then it might not have been enough and felt empty, OR, if it the map were 10 blocks smaller then maybe it would feel cluttered. But what he has going up there is a perfect harmony of decor and space. Not cluttery at all.
Then it occurred to me that you may be referring to his use of grass decoration. That's normal. Step into the wild sometime and check out all the random chutes of grass, weeds, and flowers. Personally I think his map could stand to use like a single weed decoration tile (which imo is the yellow flower one...one of them anyway) Anyways, my point is, his map is very believable. It's what everyone should want to have unless the game is some sort of odd genre.