• UPPER CLASS This is divided into three sections: royal class, which at the time was royal family and spiritual leaders. The middle upper class was for officers, baronets, and lower level lords. The lower upper class included your general rich asshole: wealthy families and large scale businesspeople that built their fortunes.
• MIDDLE CLASS Middle class is in two subsections, higher and lower. The only differentiation here was between salaries and social standings. Higher middle class was more likely to be able to secure any kind of upward mobility. Lower middle class people usually worked under higher middle class. A mid-level merchant as opposed to the person working for them.
• WORKING CLASS Working class were the hard laborers and tradespeople - the skilled class and the unskilled class. Think an undertaker as opposed to a gravedigger.
• UNDER CLASS The lowest of the low in society's eyes, we have the poor: people who were destitute and relied on the charity of others, orphans; and prostitutes, who were under much debate at the time as far as decency went. Also, they were being murdered by Jack the Ripper, so you know, ymmv.
• ROMANCE Did you know that Anne Brontë wrote what is considered the first sustained feminist novel in a Western society? Well, now you do. In this, take your main characters, watch them suffer for 300 pages, and eventually they'll realize they're meant for each other. It's all a bit gothic though, isn't it? Dreary, brooding. Sometimes awful things happen. But we've got love (sometimes) and marriage (more often) in the end.
• HORROR Did you know that a vampire is haunting this small town? Werewolves the next town over? Ghosts in every manor? Did you hear about that scientist that went mad? What kind of place is this? Maybe that masqued ball isn't a good idea.
• SCIENCE FICTION You've got a time machine, or you live in a steampunk dystopia set in Victorian times. Perhaps you have a flying machine that's quite advanced or you've traveled to the bottom of the sea or the center of the earth.
• MYSTERY Do you want to be the greatest detective that ever lived? Or perhaps their sidekick. You're not as bumbling as people 200 years from now may try to say you are. Solve thefts, catch Jack the Ripper (good riddance), do whatever! Just put your brains to the test.
• SLICE OF LIFE The simple things. Perhaps you're a lord throwing an expensive party. Perhaps you're showing off your charity by inviting the lower classes. Perhaps you're a merchant on a trade ship to another place. It's your daily life and you're living it. Just be yourself.
• FANTASY Perhaps you want something lighter. You want to travel down the rabbit hole or through the looking glass or be a princess or live in a fairy tale meeting mystical creatures.
As always, these are just suggestions and you can pick your scenario from your genre. Also, not all examples are Victorian era but we do what we want in these parts because the meme cops aren't going to get us (even though we're not them). Make up anything you want, as long as you're having fun! Make sure to post a short backstory in your top level comment so people know how to work with your AU!