Where can I find information on artworks displayed at the United Nations Headquarters in New York?

Most of the artworks displayed in the United Nations Headquarters in New York have been presented as gifts or donations to the organization. 

General Assembly resolution 63/270 of 7 April 2009 requested the Secretary-General to create a gift registry. The website is linked below.

The Library also has the following books on this topic:

1. Art treasures of the United Nations by Jacob Baal-Teshuva. New York : Thomas Yoseloff, 1964 : Call Number: UNX.700 B111 
2. A world of art : the United Nations collection by Edward B. Marks; foreword by Boutros Boutros-Ghali ; preface by Brian Urquhart ; introduction by Diana D. Brooks. Rome : Il Cigno Galileo Galilei for and on behalf of the United Nations, Dec. 1995. Call Number: UNX.700 M346, Ref 700 M346, & UNST/SG(02)/W6
3. The U.N. building : foreword by Kofi A. Annan; essay by Aaron Betsky; photographs by Ben Murphy. New York : Thames & Hudson, 2005: Call Number: Ref 341.1 U542 & UNX.232 U542.

In addition, the Library has a few internal resources to assist with this research, including the DPI Press Feature No. 214 of July 1971, titled “Gifts presented to the United Nations at headquarters”(attached)

The Yearbook of the United Nations and press releases are good starting points for research on this topic.