New units
 

Besides the viking units, are there any new units for the other races?

The only one I have seen is Jotun which is still Norse unit but considered neutral.

there are frost spiders and ice dragons, both neutral and obviously kinda related in theming.
then there is the Lava Golem, which can only be summoned by a valkyrie skill so they kinda count as viking units despite being neutral.

Rune Mages arent new but changed considerably to work with the viking runes aswell as unused hero runes.

Almost every race/unit has a subtle difference.

Archdemons can do AoE attack now with 4 reload, all demons release rage balls when killing, they also get a bonus if they hit with a critical...
Dwarves like to retaliate harder (15% bonus to person who hit them last)
Humans/Elves work better in familiar terrain (whatever terrain you have fought the most in, bonus to attack/defense stats)

A few other small details...

What CK said. You will find a lot of tweaks and ehancements to units across the board, so it's fun to discover them all and play around with it, I think.

I was hoping for more real combos to try out than the races we see already. But oh well, wonder if anyone is willing to do a mod for AP or CW later to include the Viking units.

there is a new combo with runemage+phantoming
AFAIK

but when i find some new ones i will post them here;)

Nope, Runemages always had the phantom skill.

but not with the runes;)

Yeah, like I said above they changed the Runemage considerably to reflect the rune system. Only change to the abilities themselves is that they have charges fueled by runes and ressurect was replaced by runic word.

Sucks that I always feel forced into playing humans because all the other units are meh at least to me. Vikings could be a lot more fun if someone made a increased hp mod for them.