If you zoom in on the details, an important technique that can be applied to your existing builds is sticking extra bits onto flat uniform walls to break up the colors and add three dimensional depth and shadow. After a while you'll find yourself starting with the decorative themes and filling in the flat parts between them last.

The small, framed 1x1 wooden door is hugely useful for this because it has half-unit snap points along the edges which are perfect for placing beams to stick out just a little bit.