I have used an assortment of old electronics bits from a dead radio circuit board, plus innumerable plasticard scraps of various thicknesses, and the odd bit of wire or guitar string. All have been stuck in place using superglue (cyanoacrylate).
The spine receives a pair of resistors (?) which look suitably like cryogenic tanks, and an array of plasticard pieces.
The port stern walkway side receives a small shelf with an assortment of plasticard scraps. The TV Eagles all had these small shelves inside the surrounding framework. I could have added a lot more detail here, but as they will be partially hidden inside the surrounding framework, I decided that this will do.
Forward port walkway side - plasticard and bits of wire.
Forward starboard walkway side - plasticard, guitar string. The semicircular piece was one of several hole-punched from a sheet of thin plasticard. Some were used whole, others were cut in half.
Stern starboard walkway side - plasticard, wire.
The detailing complete. Now for painting...