Look at Valve maps, or popular community maps. Think of your favorite areas on maps, with the most fun gameplay, and try to figure out their core layout. Don't copy them, but try to figure out their core concepts and then incorporate similar concepts into your map.
Alternatively, try and think up weird layouts that you haven't seen done before. Pick one you like, tweak it, and put it into your map. (I guess this probably won't work since it sounds like this is where you're already having issues.)
Finally, you could take your map theme (industrial, nature, spytech, etc.) and just think of an area that would make sense with your theme. For example, an industrial theme could get a loading dock area while a spytech theme could get a data center area. Only use this as a last resort, because it can lead to very bad layouts. Remember gameplay should always come before aesthetics.
Also, I'm really new so don't quote me on any of this