I think you have a good foundation. I would use falconperigot's suggestion an add a couple of "modeled" items in the creeks bottom. The texture you are using for the bottom right now is to clean and flat. Try adding some underwater vegetation too. I really like the texture you have on the fish. That looks very good as it is. The beaver looks good to. I think you need to add some branches to the den, (thats what it's called right?) They are mainly made out of twigs branches and mud.