It is normally not possible under Art. 34(2)(b) to add completely new drawings to an application, since in most cases a new drawing cannot be unambiguously derivable from the mere text of the description. For the same reasons amendments to drawings should be carefully checked for compliance with Art. 34(2)(b).
For drawings based on the priority document, see GL/PCT-EPO H‑II, 2.2.2 and subsections.