Candles in glass boxes - perfect combination of cozy and contemporary. Using flameless/electric candles for this would be a good idea to not have to worry about melting wax oozing into the bottom of the glass box and onto the other decorative objects
Line: The book shelf in the room shows the use of line because the book shelf shelves are built against the wall forming a miniature tree. Our eyes are drawn to look at the book shelf tree from bottom to top and outward to the tree/bookshelf branches.
Scandi Home: DIY Shelf System for the Study (I think I'd prefer to mount it to the wall vs. the leaning shown, but I do love how it looks like a large floating shelf unit - like the look of the shelves on the plywood backdrop)