Patches are embroidery you hold. Every detail is inspected up close. Designs that look great on screen sometimes fall apart at patch scale.
Keep the shape simple. Circles, shields and rockers merrow cleanly. Ornate custom shapes require die-cutting and drive cost up.
Simplify colors. 5–8 colors is a sweet spot. More adds cost and complexity without much visible improvement.
Design the border. The merrow edge is part of the design — decide its color early.
Avoid ultra-thin strokes. Anything under 1mm won't hold together in thread.
If it's a two-piece rocker set, digitize the whole set together so proportions match.