After about five months of working on them (alongside other projects), these boys are finally finished! Arms are magnetised, and pauldrons were all scratch-built from plasticard and greenstuff. Helmets were modified using more plasticard and greenstuff, and the glaive weapons were also made using... plasticard, greenstuff and some spare bits.
The bases were also custom-made using greenstuff.
And yes, I am fully aware that they're using the pre-Heresy Thousand Sons symbol. That's entirely deliberate.
As for the symbols for each terminator, they're based on which psychic discipline each one specialises in. Had to make up a couple of the symbols since there's no real descriptions of them as yet in the 40k background fluff.
Decided to make the Raptora symbol a swooping hawk - fits the overall bird theme they seem to have going, and raptor = bird of prey.
Flared wings to give the impression of a 'shield' to represent the Raptora's kine shields, and outstretched talons to represent their more offensive telekinetic abilities.
I vaguely remember reading somewhere that the Athanaean symbol was the aspect of an owl, which seems to fit. Again, fits the overall bird theme, and owls are considered wise, all-seeing and all-knowing.
The Pyrae and Pavoni symbols have been described in fluff, so those were easy enough - a phoenix and a colourful feather, respectively. And of course the Corvidae use the raven's head, but none of this squad are Corvidae, so eh.