I actually really like what you did here, terrainingwise, you cannot really get done this in a realistic way, but the way you used the nomally ugly tiles to symbolise the landscape totally looks fine for me. The tiles between the mountains on the ground might be a bit too much, and as Garshilan pointed out, the dark grass does not look the best, but if used a bit less I think this terrain is totally fine for your purpose!
Oh, and maybe add some more hills inbetween the mountains, I think it's a bit flat there.