I LOVE spanish art, here are the ones I can think of:
* El Greco - Lived in Toledo, was actually originally from Greece, but everyone thinks of him as a spanish painter. THE spanish painter I always think of first
* Velasquez - Did what was considered one of the three "most perfect" baroque paintings ever done "Las Meninas"
http://en.wikipedia.org/wiki/Diego_Vel%C3%A1zquez
* Goya - Started by painting positive, happy portraits, went into depression and painted the famous "Black Paintings", so sad
http://images.google.com/images?sourceid=navclient&ie=UTF-8&rlz=1T4SUNA_en___US203&q=goya+black+paintings&um=1&sa=X&oi=image_result_group&resnum=1&ct=title
* Murillo - Soft, religious paintings, primarily in Seville
* Gaudi - Art Nouveau artist that designed the famous cathedral in Barcelona
http://images.google.com/images?sourceid=navclient&ie=UTF-8&rlz=1T4SUNA_en___US203&q=gaudi&um=1&sa=X&oi=image_result_group&resnum=4&ct=title
* Picasso - Already mentioned, famous cubist and abstract painter in the 20th century
* Miro - 20th century
http://images.google.com/images?um=1&hl=en&rlz=1T4SUNA_en___US203&q=miro