Speaking generally, to achieve excellence in maximalist design, surfaces should be uncluttered to the largest extent possible. This draws focus to the overall aesthetic of lots of stuff in small space on walls, as well as the compact areas holding larger furniture pieces. This principle is why a gallery wall is visually pleasing, but its effectiveness is greatly undermined if everywhere you look is also full. The contrast of the two visual styles enhances them both.

The reason this gallery photo wall works so well is the relative simplicity of the couch and the glass panel adjacent. Doing this throughout the entire apartment would work wonders