tbh the tiles look a bit boring, I think you could work a little more on the colors to focus on what you want to achieve (maybe it's a happy game? a horror game? have fun with your palette). The same goes for the patterns you're using, they work fine but doesn't have much of a personality in them, the grass for example, doesn't need to be that straight, maybe you could try different patterns.
take a look at konjak's work, see how this can make grass/rocks look way more interesting than they normally are, he's really good at this you should check out his other games.