Ulm. They traditionally use that dark blue color that is on their standard. Also if you look at their units they have a cresent moon on their shields (which they only use the block shaped Tower shields). You might want to go on a variation of that.
Abysia. Red, Yellow, Black are all central colors in the Abysian units. Their starting site is the "Smouldercone" which is a volcano. So maybe something with that too.
Atlantis. Dark Blue, Aquamarine, and Coral (Pink) are common colors for atlantis. Most of their shields are "Turtle Shell Shield" maybe you can make their look like a turtle shell in some way.
Pythium. Varying colors of green. They also do alot with serpents and swamps. Perhaps making their shield snaky shaped is appropriate. (I don't like the purple of their standard)
Man. Green, Blue. Alot of association with forests and Avalon.
C'tis. Varying colors of green. I liked the symbol you had for C'tis. But they are lizards, so lizardy stuff. (If you want you can look at the Lizard Lord, where he got his bright orange jumpsuit)
Arco. They have no real prominant color. Also most of their units look rather drab ;P. It seems to be more of a society where women hold more importance, as well of course as the stars.
Caelum. Light blue, blue and white. They are the winged race. Something with wings on it would suffice or something to do with ice/cold.
Ermor. Black, Purple etc. Death and despair, et all. Just picking from the variety of symbols availiable for them is hard enough I imagine.
Marginon. Red, Orange, Black. Inquisitors and fire. Could use a classic French Coat of Arms for this and it would be semi-appropriate. Or something to do with the Chalice.
Pangaea. Green, brown, nature colors, maybe their shield could be woodish, or something else 'natural'.
Machaka. Brown, Red, Orange, Black. Spiders are of course preference here