Having some great miniatures and an actual dungeon to run through is fantastic, but to round things out it helps to have some assets present for your players to see. The reason is twofold; anything to increase the ambiance always helps but it also eliminates confusion as to where objects are during a fight. In addition, having the physical objects present can easily increase the intensity of the combat.
Take this example: Mentally set up an encounter for 5 players fighting 2 golems in a 20x25 foot library. Many of us just set up/draw out a 20x25 foot empty area with the cursory knowledge that it's a library and therefore has "books and things" in it as a pure backdrop. Did you even consider the bookshelves and reading tables that block movement and sight? Or spilled books and pushed over shelves that may act as Difficult Terrain? I had my players go through this exact scenario as shown to the right.
There are three main ways to make decorations above and beyond drawing them in; Vinyl clings, crafting*, and 3D printing*. Like everything else, I tend to use a blend of these methods in my campaigns.
The party must now carefully plan their strategy since view and free movement have now been hampered by the added decoration.