The phrase "art made known" implies the act of bringing something hidden or unknown to light. In contrast, its antonyms would suggest the opposite, such as "art concealed," "art kept secret," or "art hidden away." Each of these phrases implies a sense of mystery or privacy around a piece of art, and may be used to describe works that are intentionally kept from the public eye or that have been lost to time. Alternatively, words like "art repressed" or "art suppressed" may suggest works that have been actively suppressed or censored by those in power, further emphasizing the importance of bringing art into the public sphere.