There's three tricks to building well.
1. Cheat.
Look at existing LEGO models. Pull up instructions sets and try and adapt them to fit in Blockland if you need to. This becomes easier and easier as the number of bricks available to everyone increases.
2. Steal.
Look at an existing Blockland build and copy the elements you like off of it. See a tree or a piece of furniture someone built? Copy it and put it in your build.
3. Cheat and steal.
Once you've got the hang of cheating and stealing, you'll realize that you can do better than the people you're stealing from. There's bound to be something you don't like about someone's build. So copy it, but don't copy it exactly, copy it better than before.
Eventually you'll know what combinations of bricks go well together and you won't need to look at instructions or other people's builds. At this point you can probably just start looking at pictures of stuff and reproducing it in Blockland.
I know some people might disagree with my phrasing here, and it's partly tongue in cheek, but everyone does it at some level. It's just how art gets made in general. Even if you're not actively copying stuff off someone else, you're subconsciously doing it. Take the example of windows. There's a couple different categories that you can group almost all windows into. There's ones that are combinations of arches and windows and other bricks. There's ones that are made up of several or many different window bricks. There's ones that are made up of print bricks. There's a huge variety of ways of decorating a window, but they all have a lot of common elements. Why? It's because there's a generally accepted view of what a "good" window should look like, and people just borrowed elements off each other's windows, even if they weren't thinking about it, and making them increasingly more ornate.
And here's the thing - it's not really stealing. If you look at windows and doors and roofs in real life you'll see they're pretty similar and you can group them into different categories. There's your standard roofs that are composed of hips, peaks, valleys, and gables. There's mansard roofs (change of angle somewhere on the roof). There's roofs with dormers, there's very steep roofs that have entire floors and attics built in them, there's flat roofs with stair access and air conditioning units on top. There's curvy metal and concrete roofs that you seem from architects like Santiago Calatrava and Frank Ghery. Roofs can be made of asphalt shingles, hot rolled asphalt, synthetic materials, synthetic rubbers like EPDM, cedar shakes, slate, concrete, metal, clay, mud, plastic, straw, and dozens of other materials. You may not have seen this since most people don't climb up on roofs but it's common to pour gravel all over the top of a flat roofed building to reflect light and keep waves from wind and puddles from eroding asphalt and rubber roofs. Roofs don't have to be black or gray, sometimes they are painted very bright colors - especially metal roofs. Different materials have different textures - clay is bumpy, metal has ridges that the pieces are soldered together along, sheet metal is wavy. Then there's different things you can decorate roofs with - antennas, helicopter landing pads, lights, cooling towers and air-conditioning units, vents, wind vanes, guard rails, lighting protection systems, chimneys, roof drains, bell towers, roof gardens, decks and pools.
If you can figure out what stuff "should" look like, generally speaking, then you've you're already halfway there.
