Is your question about how you make things pretty or how to devine certain areas in your map?
Most (beginning) mappers are too much focused on creating one corridor to another corridor leading to a hall that leads to a new corridor. And thats kinda not inspiring at all. So maybe try to think in logic and give each area a identity, something believeable. It helps if you know what theme you want at the start and think of this while building the layout. It also helps to find as many cool references as you can find. You can even create aa overview of the level and drop in reference imagine with lines to certain areas so u get a good feeling of how each place should look and interact with eachother.
Sometimes corridors are a must to block seightlines, but it doesnt always have to be a tight boring corridor. Like cobblestone has this open field near T spawn/mid which is alright or abbey has a small pathway devined by a fence with behind it a open beautiful field and blabla.