I would love for this to be stickied, but I guess its up to the admin. I individually went through all the Army insignias and cut 'em out and posted them next to their corresponding rank. Hope this helps all you guys. Now you know what your shooting for, as far as multiplayer unlockables.
Level 1: Private
-- US Soldier Body
-- Head 1
-- Head 2
-- Small Helmet
-- American Standard Uniform
-- American Dirty Uniform
Level 4: Private First Class
-- UK Soldier Body
-- British Green Uniform
-- Canteen 2
Level 7: Corporal
-- British Brick Uniform
-- Grenade Pouch
-- Leather Packs
Level 10: Sergeant
-- Pouches
-- Medic Helmet 2
-- Head 3
Level 13: Gunnery Sergeant
-- Beret
-- American Camouflage Uniform
Level 16: Staff Sergeant
-- British Goggles
-- Radio
-- Binoculars
Level 19: 1st Sergeant
-- Commando Body
-- Commando Standard Uniform
-- Head 4
Level 22: Sergeant Major
-- Commando Camouflage Uniform
-- Belt Knife
-- Backpack
Level 25: Command Sergeant Major
-- Chest Pouches
-- Belt Pouches
-- Head 5
Level 28: Sgt. Major of the Army
-- Medic Helmet
-- Bedroll 1
-- Chute Pack
Level 31: Lieutenant
-- Head 6
-- British Desert Uniform
-- VTOL Pilot Skin
Level 34: Captain
-- Bedroll 2
-- Pouches
-- Pouch (Fanny Pack)
Level 37: Major
-- Head 7
-- British Helmet
-- Backpack
Level 40: Lieutenant Colonel
-- Commando Leather Uniform
-- Chest Radio
-- Shirtless Skin
Level 43: Colonel
-- Camouflage Helmet
-- Leather Backpack
-- Back Holster
Level 46: Brigadier General
-- Head 8
-- Canteen 1
-- Radio
Level 49: Major General
-- Winters Skin
-- American Advanced Uniform
-- Hip Bag
Level 52: Lieutenant General
-- Head 9
-- American Helmet
-- Commando Arctic Uniform
-- Canteen
Level 55: General
-- Cartwright Skin
-- Leather Pouch
-- Canteen
Level 58: Supreme Commander
-- British Camouflage Uniform
-- Knife
-- Head 10
Level 60: Supreme Commander [3 PIPS]
-- Nathan Hale Skin
-- Belt Packs
-- Shovel
-- Backpack
Via MyResistance.net: Cloven Skin
All Skill Points: Mechanic Skin
Finish Superhuman: Black-Ops Skin
Finish Superhuman with all Skill Points: Black-Ops Skin with Skeleton Head
ps- had to cut off the first 4, too many pics