A great gallery wall looks accidental and is anything but. The ones that fail share a flaw: they were hung one frame at a time, each decision made on a ladder. The ones that succeed were composed on the floor first, like a puzzle with a point of view.
Compose on the floor
Lay every piece on the floor in front of the wall and arrange until the grouping has a center of gravity — usually the largest piece, placed slightly off-center. Keep spacing consistent: 5 to 8 centimeters between frames reads as a collection; wider gaps read as unrelated pictures sharing a wall.
Keep spacing consistent — consistent gaps read as a collection; wide gaps read as unrelated pictures sharing a wall.
Mix media, unify frames
The richest gallery walls mix oil paintings with sketches, photographs with textiles, mirrors with prints. What unifies them is the framing: two frame finishes at most — say, oak and black — repeated across the whole arrangement.
Hang the center of the composition at eye level, roughly 145 centimeters from the floor, and work outward. Then live with it for a week before adding anything. Gallery walls, like gardens, are better grown than installed.