Arnold,
Cutting and re-routing plastic pipe is not hard, and plumbers do it all of the time. I would have the U-Shaped "Trap" on the left side cut and moved up about 6 inches, and rotated back 90 degrees so that it runs flat against the side wall of your layout, running away from the center of the layout, and have a new Y entry connector installed (into the downward septic line on the right) with the new Y also rotated backwards 90 degrees away from your layout, so that the horizontal connecting pipe that runs between the drain on the left and the septic line on the right could be run flat against the back wall.
When folks build out, or remodel basements, this type of work is pretty routine, especially when the are building in a new bathroom, with drains and toilet fixtures. (Not rocket science.)
Probably the only complication for this, that as I understand it, you live in either New York or perhaps in New Jersey, where work like this would cost a bundle, require a Union man, and probably require a building permit.
In many other parts of the country, a Master Plumber would be able to just show up, do the work in about three hours, charge $250 to $450, and leave. (Where I live, Master Plumbers only charge $85 to $100 per hour. )
As far as just making what you have into scenery, if I were doing clouds, I would try to use large bundles or gobs of processed cotton (i.e., the stuff that cotton balls are made from.) You may be able to find that on the Internet, since some people actually have a hobby of spinning it into thread on Spinning Wheels.
Or, crazy thought, but the "structure" of your plastic pipes looks somewhat like a bridge. Maybe there is a way to do a flat of the Brooklyn Bridge, with a "misty" finish, and glue it to the pipes.
Mannyrock
