Very nice composition! If you want to disguise the dividing wall I found that the green sticky clay used by florists bonds well to smooth surfaces, hardens over time and can be removed if needed. Rocks and sand can be pressed onto the sticky clay. I've used it to make small moats in trays for accent plantings. Here's a larger land and water scene with mudman that someone had custom made from a standard bonsai pot. A good friend found it at an estate sale and gave it to me. I couldn't find a tree I felt suitable to use in it so I planted the "Green Panda" cultivar miniature bamboo in it until I find the right tree.
