If you want depth then what you have to do is add depth. Currently everything in this image has a 1 edge black border. Try making the apparent face's border a pixel larger, and try ditching black all together and use a dark brown. Next what you will need to do is actually put some depth into the water. Usually water just isn't some puddle that is bordered by grass, so you are going to have to fix that aspect. Then ontop of adding some color depth to the small puddles and removing the heavy white outline, your going to need to incorporate it to be seen through the grass blades etc. So finish uyp the grass, then the cobblestone path, and then work on additional props. such as the puddles. Lastly, you seem to be trying to incorporate rainfall into this image so what your going to need to do, is actually make it look like it's raining, and not just in those puddles. Try accenting certains areas, and add a bit of heavy mild-transparent gray contrast to do so.
