Cyclops seems to only be in greek mythology, but I think it could be thematical in Earth-heavy nations (Agartha?)
About Prince of Death, how about restricting him to death-heavy nations? C'tis of all ages, Ermor of all ages, Helheim.
According to wikipedia (I know, there are better sources, but wikipedia is fastets and most likely accurate enough for this cause, it's not like we are being scientific or anything.) Manticore is from Persia according to wikipedia.
http://en.wikipedia.org/wiki/Manticore. So Abyssia would most likely be a good choice. Caelum might also be a candidate because of the Zoroastrianism (manticore also flies!). Manticore is not that powerful, so it also might be given to blood heavy nations (crossbreeds, you know), if ti spread more widely, perhaps it will see some use when it doesn't have to compete with Wyrm all the time.
About Titan. I was thinking it could be thematical for all of the following:
Skandinavia, Vanheim all ages, Giants of all ages, Helheim (Titan is a obvious Thor wannabe)
Arcosephale of all ages (umm.. Zeus, anyone?)
EA Ermor (Jupiter from Rome)
EA and MA Ulm (Germans also had Thor)
Tir' n' Og, Eriu and Man of all ages (thunder god fits their style)
Caelum of all ages (fits their style and it allows them to dip for earth magic)
I assume that you will restrict the rainbows according to paths? That only frost/water mage nations will get Forst Father and so on?