I put these rules together years ago for a WFRP game. The basic idea was to reflect the fact that, while a starting career reflects what you did as a youth/adolescent/young adult, your childhood might have been spent doing something quite different- and the Old World being the place that it is, you probably picked up a few things in order to keep yourself alive. It also provides a little mechanical support for some interesting character concepts, like the former wealthy burgher who was reduced to thieving or banditry, noble children dumped into the church or university system, thieving urchins who went on to lead respectable lives, etc.
Background (Optional Rule): Select one of the following backgrounds at character creation. Your background can't be changed once it is selected.
You grew up in one of the many lower-class neighborhoods of a city or town. Whether you were the unsupervised child of long-suffering laborers or an orphan adopted into a street gang, you spent a fair amount of your childhood on the streets with other children. Young children are often employed by criminal organizations as pickpockets and lookouts; even children with less colorful backgrounds probably swiped a hot pie from an unwary street vendor a few times. Children who live and play on the streets often develop fast hands and quick wits, and a knack for making a quick escape- whether from the Watch, or just an enraged pie vendor!
Skills: Sleight of Hand
Talents: Alley Cat or Streetwise, Flee!
Like most of the children in the Empire, you grew up in the great outdoors, in or near a farming settlement. Farm children don't live the idle lives of city kids; they're expected to pull their weight around the farmstead, feeding and tending to the livestock, gathering plants, and doing light work in the fields such as weeding and sowing.
Skills: Animal Care, Trade(Farmer)
Your parents were wealthy enough that you didn't need to work as a child- a rare privilege among the people of the Old World! Instead of plodding in the fields or swiping coins from unwary merchants, your parents ensured that you received an education of some sort- either by hiring a tutor or sending you to one of the small schools run by various religious orders and guilds. As a result, you know how to read and write, as well as more about the world around you than the average Imperial citizen. You're also accustomed to having to part with a little cash in order to get anything done- a concept very foreign to many rural Old Worlders.
Skills: Read/Write, Haggle, Common Knowledge (The Empire)
You're a bona fide member of the upper crust, with the background to prove it. Of course, your family may not actually have any land, wealth, or income, but you have your good name, by Sigmar! Whether lording over vast estates from a townhouse in Altdorf or barely making ends meet as gentleman planters, the nobility ensure that their children know a thing or two about their heritage and their status. Deriving from the ancient custom of nobles being horse-born fighters, they teach their children to ride (walking is for peasants!) and how to properly interact with other members of the upper classes. They also provide the children of their household with the family insignia, as a means of identifying themselves to other nobles or authenticating messages from abroad.
Skills: Pick two of: Ride, Read/Write, Charm
Trappings: Signet ring with family crest (worth 1d10 GC)
Your family wandered around for most of your life, perhaps working as peddlers or plying their trade on one of the Old World's great rivers. As a result, you traveled more as a child than the average Old Worlder does in a lifetime, and have picked up a variety of bits and pieces of information about the wider world. You're also used to having to figure out your way around in new places.
Skills: Pick two of: Row, Drive, Sail, Navigation
Talents: Seasoned Traveler
Your family worked a trade, either as artisans in a city or town or among rural folk. You were expected to help out around the shop as a young person, and as a result have picked up a bit of the family trade, as well as a knack for recognizing good workmanship when you see it. You've also learned the find art of negotiation by observing your family at work.
Skills: Haggle, Trade (any one), Evaluate
Whether you were literally an orphan or not, you were raised among the sounds and smells of a temple or monastery. Maybe your parents were clerics, or perhaps you were just sent away for a religious education. Religious institutions tend to provide very specialized forms of instruction- while the basics of literacy are covered, most of the emphasis is on learning the tenets of religious doctrine. You also probably spent a fair amount of time singing and chanting as part of regular religious services.
Skills: Academic Knowledge (Theology), Perform (Sing), Read/Write
Rather than living in a typical village or town, your family lived deeper in the woodlands. Your parents may have been Woodcutters or Charcoal Burner, or just anti-social hermits who preferred to keep to themselves. You probably learned to hunt or trap as part of your upbringing, as well as how to keep out of the way of the wildernesses' more dangerous occupants.
Skills: Set Trap or Follow Trail, Outdoor Survival
Backgrounds for Non-humans
Halflings can use any of the human templates.
Dwarfs most commonly use the Trades or Educated Urbanite background. Dwarven nobles use the noble background. There are very few Dwarven Drifters, but it might be possible within the Empire.
Elves living among humans are often employed as negotiators and traders, in which case they typically have the Educated Urbanite background. Wood Elves are almost always from the Woodlander background.