Paldroons/shoulder-armor definitely help "sell" a variety of different minis, starting with sci-fi, and going on to heavily-armored fantasy paladins and other warriors, and moving these days into tactical body armor.
Mixing in some capes and mantles in different materials, genres, and styles is a great idea.
Maybe include some gorgets and ruff collars as well - these sorts of things work about as well as capes and mantles do (that is, they don't fit all minis, but they fit enough to be useful and when they do, it looks great.) Similarly, the scarves that came with the French Resistance have turned up in a couple of projects - those are great as well.
Bonus points if there are a couple collar bits (whatever these are called) loosely inspired by those worn by the Time Lords from the old Doctor Who series - those costumes, like the Daleks, were one of the more inspired production/costuming design decisions from the show, and really helped sell the Time Lords as an ancient chapter of space-wizards - combined with some robed torsoes (from, say, a hooded/robed monk/cultist kit!), this sort of thing would work great in both sci-fi and fantasy for designating leaders (especially villain masterminds, wizards, necromancers, and other dramatic types of characters):
Anyway, things like shoulder bits, capes, collars, and such are sadly neglected in multi-part miniatures kits for adding a distinctive touch to specific characters or factions, and, along with humble ray-guns or bolters of some sort, can instantly transform historical figures into a Death Fields or other sci-fi faction!