So I started off by sculpting mud in Zbrush just as you normally would. Getting some cool shapes and some height variation into the texture. I then sculpted a few rock subtools which I placed around the mud in different areas.
For the grass, I created this little guy in Maya and brought it into Zbrush to start working with.
I duplicated the subtool of the grass multiple times, rotating and scaling it all over the mud. Then combined all of the grass subtools and did some quick pushing and pulling with different brushes.
After I finished the sculpt I exported the height map and brought it into photoshop. So here is a quick image of how I created the puddles within photoshop.