Yup, that's a common error: misuse of the tileset. That bridge was made for being over water, and shouldn't be used elsewhere.
Another thing too: the red sign was meant to be a red sign, not some kind of door lol
The last thing, more concerning the tileset you're using: the flowers and the sand should blend with the grass, however, I can see a light green square.
Oh, one more last thing... (sorry)
there are 5 tiles for grass in Pokemon, but you're using just one, making the floor look too repetitive, you know?
That's about it, I guess...