More objects are good. Going to second the suggestion to look at the scaling of the backhoe -- it looks a little big. The portajohn also looked a tiny bit big, but I checked some specifications for a real one and it was fine. Doing a texture swap on the WCW Billboard will be more annoying than difficult, but the warning is appreciated.
As far as the 2D objects are concerned, I think what you'd need to do is have the trees billboard, which is simple to do, but kind of annoying.