Not much to suggest about...
What's the religious motiff you are aiming for? Viking, Celtic and Saxon were all quite different religiously and philosophically, so while I can give suggestions regarding each of them, I'd need to know more about your campaign religion first.
Off-the-cuff, though, I'd suggest making the Spell List for the base class more "Gray" than Black/White, using Prestige Classes to distinguish the two better. This adds a certain distrust from the common folks, whom will see some spellcasters, those of known affiliation/position/status, as allies, while everyone else are people that should be avoided, at best, or nailed to a tree and burned to death (at worst). A few Good/Evil spells should be included to set a standard (Good Prestige Classes require a lack of taint, while Evil Prestige Classes require some degree of it.)
(Aside: Each of these had "old crone" figures in some of their myths; You may consider determining the Racial Levels for Hags and then alter them into full Prestige Classes for tainted female casters. I've been considering doing similar myself...)
One thing to note is that each culture you listed as an influence were warrior cultures
(especially the Vikings and Celts)
, meaning that even the common folk could fight, although only the nobles were exclusively combatants. I have a Base Class somewhere meant to represent Celtic citizens, which had +1/1 BAB, better Skills, and cultural-based Features, but less Feats (Nobles would have been Fighters by comparison, although those less snobby would likely have had a few levels of this class just to know the basics of managing their communities, and the "call on Kinsmen" feature would have been appropriate for them as well). I can dig that one up, exctract and OGL it and send it your way... (Come to think of it, it was in a 2-part article in a free d20 Ezine; I can send those both your way if you'd like.

)
If leaning towards Celts, I'd suggest looking into Chariot combat rules (
Sword & Fist and
In the Saddle both have good systems for that*).
Ink & Quill (Bastion Press, Free Download) has a Warrior-Poet Prestige Class that is rather nice and fitting to a Celtic milieu as well. Magic (AEG) has a tattoo mage; This class (or the simple concept of it) can be combined with Celtic-style tattooing easily enough. Slaine (Mongoose) is also supposed to be Celtic-flavored, although it's also based on a comic book, and not having seen it, I can't recommend it personally, but I have heard good things mostly. Check the review at the main d20 Reviews page.
If leaning towards Vikings, I'd suggest building your magical flavor around Runes and runesmithing. There are several sources available of such, but it also wouldn't be hard to do on your own and possibly only with flavor changes (spell preparation = enscribing a rune into a stone, etc.). Although, having a runecaster akin to a Sorcerer using the "recharge" rules from Unearthed Arcana would also be a way to go (with the time applied to the stone instead of the caster, but with the same in-game effect).
(Come to think of it, the Recharge mechanic can also be applied to the tattooing concept mentioned above.)
Someone more knowledgable on the Saxons will have to make suggestions regarding them; My knowledge is scant and mostly during the "Robin Hood" era, which is some time after their cultural height (as an independant people, that is) and long after the Vikings and Celts had become assimilated into other cultures or withdrew far to the north and west into Scandanavia and Greenland. IIRC, though, Saxons were excellent bowmen (ala the foundation of Robin Hood being a marksman in a "Saxons are the best bowmen and Robin is the best Saxon" kinda way).
Beyond that, I'd need more by way of target flavor and setting specifics (religion, culture, frequency/power of magic items, etc.) to suggest anything more specific.
* I've not seen
Complete Warrior; Did the S&F Chariot rules get a 3.5 update in that book or were they left behind? Apart from that, if "OGC-ness" is important, go with
In the Saddle.