the general way to make a good tileset/map (wow, that's a heavy opener!) is to divide things up nicely:
3 parts fill tiles, these are your basics that will join everything together.
2 parts signifier tiles, these do important things like direct the player or further define the setting.
1 part eye-catchers, these are tiles which make things pop out, whether they serve a function (cave entrances, puzzle markers....) or just liven things up (the occasional splash of color).
These are not rigid measurements, more for emphasis. a simple game might have say, 1 wide fill tile, and maybe it's just a flat color, but if that's the case it should be the most considered color in the set. Signifiers are also important, but should be secondary to the fill - it's most important for a player to see where he can go, not where he can't. Don't forget these though, they breathe life and information into the setting. I also recommend not putting too much more energy into your eye-catchers, because a great tile/object in the middle of a bad set is still a bad set, and you can also risk what a lot of games do where you throw down an exciting tile every few feet to make things 'cool,' when really all you get is a busy, uninformative map.
Right now you've got a lot of eye-catchers trying to be fill tiles by using the materials of the road. they're sharp-lined and singular, and contrast highly with the road. Rather, try making shapes which aren't so contrasted, but blend a little better, and meet the edges so that they can flow into each other to create new shapes
.
