The 2 first glyphs are a given, Glyph of Frostbolt (even with the chill effect removed, it can still proc Fingers of Frost) and Glyph of Molten Armor, nothing like crit rating.
So I am stuck on the last slot, basically.
Here are my choices:
Glyph of Eternal Water : Makes the Water Elemental summon permanent. This is pretty sick for PVE, with the recent boost to Water Elemental's waterbolt's consumption (reduced by 80%), they can spam their spell pretty much constantly, and by the time they run out of mana, you can summon another.
Glyph of Fireball: With my spec, I can summon the water elemtanl every 2 minutes 15 seconds, while is plenty for bosses. I have a talent called Brain Freeze, which gives my frostbolt a 15% chance to make my next fireball spell instant and cost less. With this glyph, I'd have an addtional 5% chance to crit with it.
Glyph of Mirror image: Makes a fourth image spawn, so that would technically increase the DPS if the Spellpower is still split at 33% per image.
I did not bring Ice lance in the choice because even with all the talents, Ice lance still does less damage than a Frostbolt/Deep Freeze combo would do during a Fingers of Frost proc. Also, while chaining the 2 Frostbolts, there is a chain to refresh the buff, something Ice lance cannot do, which can increase damage further drastically.
Basically removed all points from Brain Freeze for 1 point in Improved Blizzard, something I completely ignored and lately realized it procs Fingers of Frost like mad. Only thing I've yet to notice is if blizzard can use Finger of Frost charges.
2 points into Enduring winter for the 66% to proc some mana regen for the whole party/raid, since this can't proc more than once every 6 seconds, and frost mage is basically just spamming frostbolt, I don't think it's even useful to max the talent.