Fantastic Ripley, I like how you sculpted the edges to take away from the hard straight lines. My suggestion for the right side is to study up on making a large mountain with tracks that run around and through it. Then you can landscape it with trees viaducts, waterfalls.
If you don't want to drill into your walls and damage them with screws to sturdy the table tops and prevent them from moving you could try what I do a lot. Use these command strips but stick them on horizontally along that top rail and lock the whole think to the wall and easily removed if you have to. I have a whole drawer full of various Command Strips as they come in handy. https://www.command.com/3M/en_US/command...318&rt=rud
If you don't want to drill into your walls and damage them with screws to sturdy the table tops and prevent them from moving you could try what I do a lot. Use these command strips but stick them on horizontally along that top rail and lock the whole think to the wall and easily removed if you have to. I have a whole drawer full of various Command Strips as they come in handy. https://www.command.com/3M/en_US/command...318&rt=rud