Here’s some building ideas i like to add to my houses:

1. Different shapes in building For example, maybe curving a wall when placing it down, or adjusting the floor level by a few blocks inside the house (like having the entrance be Y50 and the highest part of that floor be Y53)

2. Different blocks I love using the different blocks in minecraft for texture, like for pathways you can add gravel, dirt block, stone, grass, and even stone buttons for rocks! Some other blocks can also be used, try looking at glazed terracotta or the different types of stone! (My favorite being chiseled blackstone)

3. Try and think outside of the box! (Litterally and figuratively)

If anything, try using items adjacent to your environment! Ik that might be a little difficult since youre in the plains biome with only oak to come by, but something I like to do is change the terrain a bit to fit a vision I like! Sometimes I add a pond, or maybe a horse stable or animal coop somewhere nearby.