Hunt flea shops, yard sales, and thrift stores for technologically irrelevant speaker cabinets and well-built, vintage suitcases. Be sure to get a variety of sizes but aim for relatively squared shapes so they nestle together well. In our case, we needed about 20 speakers and suit cases.
As a starting point I brought along part of the original furnace from DIY Network Blog Cabin 2014, which could house the system components and amplifier. For your project, start in the center and spin and rotate the shapes to find the best fit with each box nesting to the other.
Some of the boxes may be too deep to match the others so plan on making cuts. Because these boxes could be a mix of wood, cardboard, steel, and other materials plan cutting carefully. It may take a circular saw, jigs saw, or rotary tool to make a clean and safe cut. Be careful of flying debris and other snags along the way.
To top it off, cut a plywood top following the edge of the system. Give it a slight overhang and then stain and seal it.
Not only is this an easy and eclectic entertainment system, but the speakers can also be wired to the sound system for interesting and functional built-in.