Spain, Elvira, city. A decree of the council of Elvira in 300 provides the earliest testimony to the iconoclastic tendency of the early Christians.
Spain, Cuenca, Cathedral: 14^th century icons.
Spain, Madrid, National Library, Byzantine and post-Byzantine manuscripts, including Skylitzes ms.  from 14^th century. See http://en.wikipedia.org/wiki/Madrid_Skylitzes
Spain, Vich, Episcopal Museum, textiles.