With a Trench Coat as the "Top", it is not possible to have a Fanged Skull or Small Skull as your belt with the "Normal Male" body type, they don't even show up.
However, both the Fanged Skull and Small Skull on the "Female" or "Huge Male" body types show up and can be selected as a belt with the Trench Coat selected.
Clearly, a missing costume piece that should certainly be fixed when possible (given that y'all are busy and such. just figured I'd let y'all know.)
Thanks,
Stitch
So, since there's no bug section (yet :P ), I found a bug in one of Eagle Eye's missions as a Peacebringer, where when you're infiltrating the Skulls (Skulls are friendly in this mission), the Quantum Gunners that spawn will still act hostile, and attack you on sight, possibly preventing completion of the mission if the Gunners spawn anywhere on the path to objectives.