These images come from the Koninklijke Bibliotheek who are nice enough to provide these images to the public. I can safely say that all the images below are pre-1500 (one is even pre-1400) and come from Books of Hours, the "best sellers" of the medieval period. Every example of a bagpiper happens to be from the "Annunciation of the Shepherds" portion of these books of hours. I wouldn't necessarily base a replica instrument on any of these but to see them in a group all together can either show generalities in the instruments of the time or provide evidence for severe medieval plagiarism!
Click on the images to make them bigger or reveal the full picture.