How can I hide or dress up a large wall of debris?
Plant desirable native shrubs and vines that would grow over the irregular surface and transform it into an aesthetically pleasing feature. You might have to add soil to fill voids, and you could mix leaves into this soil for fill.

You could put up a barn owl box to entice one or a pair to live there and provide natural rat control. If you don't have barn owls where you are, then you probably have screech owls. We have had boxes for screech owls in our back yard for almost 40 years and they do some rat control, but not like a barn owl or barred owl would.  

Have you had any suggestions that in the current condition your yard is not in compliance with residential code? We have a natural yard in a sea of manicured lots and we have gotten three citations for code violations over the past 10 years. The underlying criticism is that our lot (10,000 sq ft) is not neat and so surely must be in violation.

The code inspectors have so far ruled that our yard is in basic compliance under the xeriscape allowances in the city code, but they always find one or two technical violations or common violations that are mostly overlooked. Last time the only thing we had to do was trim trees in front to be above 14 ft from the street surface.