what sort of spells would you make based upon the upcoming holidays?
Jingle spells
Everybody sing along...
jingle spells, jingle spells, jingle all the wayyyyyy
oh what fun they are to cast on a cold midwinter's dayyyyyyyy! 
Abysmal flames, hear 'em singein',
Hedge wizards, see 'em cringin',
A simple song we sing,
as fires we fling,
Walkin' in an Ignem Wonderland!...
Presenting a jingle spell, for the genuine christmassy spirit:
Cursing the Thief
Muto Imagonem 15
R:Voice, D:Month, T:Ind
This spell causes the targets cheek to appear branded like a convicted thief, and makes him jingle as he moves, as if he was wearing a harness of bells. Both these effects can make it very hard for a proper thief to make a living. Cast during winter to make the next month extra hard on the target, and combine with a Phantom Gift with extended duration (month) for the indirect effects to be extra cruel on an already poor target.
(Base 2, +2 Voice, +3 Month)
Deck your foes with balls of fire
falalalala lala la laaaa
keep it up till the expire
falalalala lala la laaaa
Don we now arcane apparel
falala lalala la la laaaa
toss the carcass in a barrel
falalalala lala la laaaa
--Ancient Flambeau Carol
Irenaeus, remind me not to offend you in the next tribunal 
You are most cruel on poor fellow criminals, sir
Cheers,
Xavi
Indeed. Id be more inclined to use a lower base MuIm spell to make them look like ol Santa and a Cr or MuMe chaser to incline them towards passing out as gifts all their ill gotten gains 
Rego Aquam
The Snowy Surprise
R: Touch, D: Momentary, T: Individual, Level 10.
Gathers and shapes a sphere of soft, lightly-packed snow and throws it as a projectile (See HoH:S) towards the designated target. This spell was intended for winter fun and so inflicts no damage, although some bad-tempered magi have been known to make use of a nasty and painful variant "The Slushy Surprise"... There is also rumored to be a variant that drops four-hundred pounds of snow on the victim's head.
(Base 4, +1 Touch, +1 Unnatural
Rego Herbam
Apprentice's Lament
R: Voice, D: Concentration, T: Individual, Level 10.
This spell animates a birch twig causing it to strike the target for as long as the caster concentrates. The twigs are too small to inflict any actual damage, but repeated blows may be painful enough to cause fatigue penalties as per scuffling at the SG's discretion. (If necessary, determine hits as per SotAB).
(Base 3, +2 Voice, +1 Concentration).
Creo Imaginem
Boiled in His Own Pudding
R: Voice, D: Diameter, T: Individual, Level 5.
This spell targets the senses of smell and touch to create the sensation that the target's pants have been filled with warm, fresh Christmas pudding. This spell was designed for yuletide humor, but has also proven to be an effective distraction.
(Base 2, +2 Voice, +1 Diameter).
Why, thank you! I will remind you, but it is probably not neccesary. As my name implies, I am fairly peaceful.
As for thieves, though, ask yourself this:
What is the point of being a powerful wizard if you can't curse people who takes your stuff.
Anyway this is medieval christmas. Passing out gifts seems all wrong. Prehaps a spell to cause fasting would be appropriate, or self-flaggelation?
Is your magus named Scroogius by any chance?
Santa's ride
ReAn(He) 35?
You can direct your sleigh and up to eight reindeer to fly with good speed. A concentration roll of 9+ explains why the sleigh does not fly in all stories and a finesse roll of 9+ explains why there is damage to roofs in wintertime. The trail of tiny stars is purely cosmetic.
Base 10? +2 voice, +1 conc, +2 group
In Saint Nicholas' version of this spell, the nose of one of the reindeers turns red.
Think you'd need a Terram req for the sleigh, no? Without it i should think the sleigh would be hanging vertically like a ball and chain behind the struggling airborn reindeer
I considered a wooden sleigh, but why not add in Terram while we're at it.
If you make an airodynamic sleigh, the speed of the reindeers might keep it in a sort of normal position. But those depictions of Santa don't appear very aerodynamic to me (although Santa has a nice droplet shape).
Ah yes, wooden would work so mea culpa for failing to appreciate that previously (not a morning person).
As for aerodynamics, I would venture that this is not exactly an "in paradigm" concept to any sufficient degree at any rate.
Saint Nicholas Surprise
Rego Vim (Creo,Ignem) Level Gen.
P:Touch, D:Sun, T:Ind
This faerie spell must be cast on a fireplace. It is basically an exotic version of a magical ward, with more expeditive effects. Any divine being of divine might less than (level of this spell-5) attempting to enter the room through the fireplace is set on fire and violently spit out the same way it attempted to enter.
(base gen)
Somehow I would say that this spell shouldn't work on Christmas day, due to the overwhelming force of the dominion in any house that actually believes in the Lord Christ.
But surely Santa is of the Magical Realm! Even as St. Nicholas, he's hardly a spiritual figure in that role. He's almost more like a house-faerie or something, (if a very round one.)
Right, right. This spell is both very unlikely to work, and likely to be an anachronism in mythic europe. I am not sure if the "coming through the fireplace" story was this early.
Anyway, Santa could be of magic, divine or even faery realm.
I think the appropriate figure would be "Father Christmas", who had less to do with chimneys (Oy, what's a "chimney"?) or children or presents, and more to do with the spirit of the season.
A carry over from more obscure and unrecorded pagan traditions, he was adopted as a christian custom as the Midwinter season became less about Solstice and more about Christmas.
So, he's a Magical (Demonic???) figure who's been adopted by the Dominion - i.e., anyone's guess.