Collecting all skins and customizations

I found several class and vehicle skin upgrades/customizations/unlocks, e.g.:

Do they carry between games? Do some always drop in the same locations? Do they always appear in the same places or after the same quests? If so, what and where are all of them? What do I need to know to collect the whole list?

Solution 1:

Most customization rewards are for your current class, but you can pick up/activate other classes' customization items. Skin collection progress carries between characters. Activated skins show as "Already Unlocked."

^{This wiki is a work in progress—modify the listings if a skin isn't class-specific.}

Mission rewards

• Shielded Favors
  • Sting Like a Bee (Assassin skin)
  • At Arms (Commando skin)
  • Amarillo (Gunzerker skin)
  • Mellow Yellow (Siren skin)
• Symbiosis
  • Blast Shield (Assassin head)
  • A Sense of Dread (Gunzerker head)
  • One-Eye Spy (Siren head)
  • Grizzled Veteran (Commando head)
• Plan B
  • SDU Weapon Equip Slot
• No Vacancy
  • Streamlined (Assassin skin)
  • Loud and Proud (Siren skin)
• In Memorium
  • Punk (Assassin head)
  • Bowler Badass (Gunzerker head)
  • Nevermore (Siren head)
• The Cold Shoulder
  • Salvador SMASH! (Gunzerker skin)
• Statuesque
  • 3ng13 (Assassin head)
  • Top Card (Gunzerker head)

Challenge rewards

• "Boom." Level 3 (explosive damage)
  • Torgue Explosiveness (Assassin skin)
• "It's Not Easy Looting Green" Level 3 (get green items)
  • Preying Mantis (Siren skin)
• "Whaddaya Buyin?" Level 3 (Eridium purchases)
  • Green-Eyed Monster (Assassin skin)
  • Greenblood (Siren skin)
• "Open Pandora's Boxes" Level 3 (open lootable objects)
  • Blue Bot (Assassin skin)
• Aggravated Assault Level 3 (assault rifle kills)

Misc.

• Moxxi slot machines (get triple 7s)
  • Vladof Sickle (skin, all classes)
  • Tediore Customer Service (skin, all classes)
• Marcus weapons vending machine "Item of the Day"
  • Dahl Elite (Assassin skin)
  • Jakobs Old-Fashioned (Assassin skin)
  • Torgue High Octane (Assassin skin)
  • Bandit Blood and Rust (Gunzerker skin)
  • Hyperion Honor (Gunzerker skin)
  • Tediore Low Price (Siren skin)
• Vault Veteran Rewards (detecting a Borderlands 1 save on your console)
  • Vault Veteran: Arachn1d (Assassin head)
  • Vault Veteran: Lancer (Commando head)
  • Vault Veteran: Sledgehammer (Gunzerker head)
  • Vault Veteran: Dr. Crazy (Siren head)
  • Pandoran Legend (all classes skin)
• Special edition
  • Special Edition: F0rg0tten (Assassin head)
  • Special Edition: Snowblind (Commando head)
  • Special Edition: Private Eyes (Gunzerker head)
  • Special Edition: Clean Shave (Siren head)
  • Special Edition: Fired Up (all classes skin)
• Enemy drops (random?)
  • Honey Hive (Bandit Technical skin, found in Southern Shelf Bay)
  • Burst Fire (Assassin skin, found from ship boss in north Southern Shelf)
  • Alabaster (Bandit Technical skin, found in Southern Shelf Bay and Tundra Express)
  • Infrared (Bandit Technical skin, found in Southern Shelf Bay)
  • Volcanic (Commando skin, found in The Dust)
  • Blue Barber (Runner skin, found in Southern Shelf Bay and Tundra Express)
  • Spilled Paint (Runner skin, found in Southern Shelf Bay)
  • Splatter Burst (Runner skin, found in Southern Shelf Bay and Tundra Express)
• Lootable objects (random?)
  • Blood Bank (Runner skin, found in a Bullymong pile right outside Liar's Berg)
  • Sky Runner (Runner skin, found in a Bullymong pile within Liar's Berg)
  • Splatter Burst (Runner Skin, found in a Bullymong pile in Liar's Berg graveyard)
• Don't Remember
  • Root for the Home Team (Gunzerker skin)
  • Woe in the Dark (Gunzerker skin)

Solution 2:

You can get them from chests,containers,from breakable and destroyable objects,enemy/boss drops,slot machines and they can be found in shops as "Item of the day".You can also get some from quests and challenges.

Yes,they do carry between all characters you have on your profile.

You can also get "Borderlands Veteran" heads and skins for all classes if the game detects a save file from Borderlands 1 on your PC.