JStor is an excellent source for Art History papers as it has academic articles that date back to the 19th century. Be cautious of articles that are book reviews--these are not sources for your paper, but can lead you to excellent sources.
Access to full text periodicals-- contemporary academic journals, magazines, and newspapers and historical newspapers (New York Times, Los Angeles Times, Washington Post, and Wall Street Journal).
This database is worth a look, but is not necessarily heavy on art history journals. It might be better once you have a list of references you are trying to hunt down.