Seems like a good gallery wall needs 1. Something larger 2. Something graphic, if not multiple graphic elements 3. Some black and white images 4. A non-traditional frame 5. Some frames/mattes that do match
What a great way to unify an eclectic mix of artwork and to keep the focus on the art by using fine black frames. The placement of the artwork (low and centred above the armchair) is also important in terms of the staggered edge in helping draw the eye into the room.