I love asking world-building questions and giving topics to think about, so I’m here to overwhelm you 
Language (what do the letters look like, what is the grammar structure), dialects (different between poor and rich, different regionally, different depending on the race or availability of education), slang (same thing as dialects, and maybe even differentiate between generations)
Environment, climate (climate change, too, over time), species in each climate (ones that are wild, that are cattle, that are domestic, that are pets, etc.), and different plants in each climate (edible, poisonous, main crop they eat, popular in the region, a nice snack, and think about how they are planted or harvested and how much is going around etc.)
Education system (who goes to school to learn to become what, what can they learn, when do they enter school and when do they graduate, is education thought of highly or not so much, and how do all the testing systems work, and are there many different types of education methods (like going to school, going to a castle to learn under a knight, or being home-schooled, or being taught by a tutor…etc.))
Not just what the clothes or houses look like but what they’re made of (materials like where do they get them? Who makes the clothes or the yarn or the thread? Who makes the houses and the materials needed for the houses? Are some houses made of different things depending on the climate or environment or the class of the person? How big are the houses? What are the clothes like when it comes to material differences with different classes?)
Politics/government (who rules and how long are they allowed to rule, is there voting or not? Do people have a say in who becomes the leader? Is there a caste system or a class-based hierarchy? What exactly does the government or rulers get to decide? How does the economy work and how much power to the top guys have? What about in religion? What about in the things people eat and wear and say? Are there practices or words or books or clothes or recreational activities banned because of the top guy? Have there been revolutions or movements in history and what were they for? etc…)
And then, with all of these, you also think what all the above would look like in the different genders, and across different species.
If you’re wondering how I came up with all this stuff, if you take any world-building item like “politics” or “religion” or “environment”, there’s always ways to break them down into little bits to find even more things to think about. That’s how I came up with those 
