I haven’t actually done the head of a pin calculations yet, but I can tell you for a fact that you can fit pretty much all of them in your pocket. The global digitization of archives continues apace, some of it backed by corporate or institutional funding, some of it the work of enthusiastic individuals.
Here’s a brief roundup of some online archives of Spanish graphic design that I’ve recently come across.
Josep Artigas – Dissenyador Gràfic. Josep Artigas i Ojeda (Barcelona, 1919-1992) was one of Spain’s major post-war poster designers. Some biographical details are here. (in Catalan). This archive is managed by Memòria Digital de Catalunya (MDC).
Also on the MDC catalogue:
Cartells del Pavello de la Republica (mostly posters from the Second Republic and Civil War).