Find a suitable royalty-free photograph of a peacock. Check for good composition and defined elements. Use masking tape to secure the picture to your work surface. Center a sheet of tracing paper over it, and secure it in the same way. Trace the basic lines in pencil, ignoring fine detail.
Assess your drawing, ensuring all lines meet up. If you find L-shaped or hourglass-shaped pieces, erase those lines and convert them to regular shapes. This is your basic pattern.
Once your basic pattern is set, remove it from the work surface, and tape it up against a wall. Stand several paces away to get the overall effect.
Check for unduly thin sections, and rework them to prevent glass breaking later on. Rule out pieces that are too small or irregular to cut, and get rid of excess lines. Having too many lead lines converging to one point is unworkable and creates solder lumps. Revise impractical angles, keeping the cutting and soldering in mind throughout.
Once your pencil outline is both practical and aesthetically pleasing, go over it with a fine-tipped black marker. Keep the lines smooth. Erase remaining pencil marks, and number each piece. Photocopy the design, and using pencil crayons, roughly color the pieces. Assess the result again.
Experimenting with cropping before you start is a good idea. Use the tracing paper as your frame, and move it over the image to find differently cropped compositions. If you want to use the peacock tail pattern instead of the whole bird, focus on a section to copy and repeat.