For original ideas and concept, I collage inspiration photos from similar things.
If I’m making a low poly police station, I’ll google cliparts or look for low poly games/models that fit the criteria. Oftentimes also I find myself joining Roblox (for this example, looking at Jailbreak could work) and drawing inspiration from there.
Once I have an idea of what I’m doing, I “graybox” my build. This is just roughly planning out the shape with colourless/textureless parts until it’s properly scaled before detailing.
If however, I’m making something from reference photos (typically smaller/more detailed things like vehicles) I’ll import pictures into studio and scale those appropriately, and then base my creation off of the imported image. This’ll help me get the details right and the proportions correct also.
Depends on the build, if it is some kind of facility with many hallways I always start with the base hallway to get a feel for the aesthetic of the map. Then I create a mini layout within studio using simple bricks to map it out and go from there. With other maps for example a military base I will find real-life references for the specific buildings then I always look for lighting examples and aesthetic examples that I like or in the case of a commission that the client likes. I apply these concepts to pretty much any build.
Like most others are saying I use inspiration from photos I get offline. It really depends on what you’re building though as if your building something that’s never been done before then you cannot really get inspiration.