Although I don't possess this quality myself, extreme attention to detail is a trait I find admirable in others. Take this project from Jan DiCintio of Daisy Janie, for example. When planning her arrangement, Jan made a "map" of sorts by converting all of her frame sizes into proportional pieces in Illustrator, then played with them until the group looked pleasing to her eye. She even color-coded the dark vs. light frames--genius. If you're not handy with design software, Jan suggests doing this by-hand using graph paper and scaled cut-outs.
Do check out Jan's full post for more tips on how she pulled off this lovely gallery wall.
(Images: Jan DiCintio)