I pack some zipties, ranger bands, wire, duct tape, needles/thread, hose clamps and super glue (depending on which bag). But I like the idea of adding a few assorted fasteners as mentioned about.

Of course, having a multitool (or Desperado's kind of hardware!) would make it easy in certain environs to liberate a nut or screw in an emergency. ;-)

Regarding screw eyes, I don't know...nothing quite creeps ya out like looking in a dark possibles bag and seeing two unblinking screw eyes staring at ya.