Go Bilbao, San Sebastien, Pamplona, Zarragoza, Logrona.
Madrid or Barcelona good but busy.
South of Madrid is full of idiots with no class or culture of there own.
East coast is full of Guiri`s and tourists. Barcelona included.
Galicia may be too wet a quiet and lacking your artistic needs.
My choice is money no issue would be San Sebastien, great food, culture, close to southern France. The north is the brains region of Spain, full of culture and class. Also great for out doors, really good for painting.
It where the educated Spaniards holiday when staying in Spain.