Couple questions, what kind of view do you intend to use? Is this typical top-down of most RPGs?
I don't know if it's intentional or not, but you have an odd thing in your grass tiles where you've used smaller, 1x1 pixels next to the double-sized pixels. It's not forbidden to do this, but it looks inconsistent and isn't something you would see anyone around here doing.
I would encourage you to put these different elements into a mockup. I always make mockups when I do tiles, and I think it's a good practice that lets you realistically see how they would look. It's also helpful, because it makes it easier to separate the foreground(trees, player, certain walls) and background(grass, dirt) tiles. It's very common to see someone start off with grass tiles, and make them super-contrasty and brighter than the player character and other foreground objects.
