An extraordinary photographic exhibit here has signaled that the great Chinese political villain of the last 13 years, former president Liu Shao-chi, is returning to favor in a major revision of official Communist Party history.

Three pictures of Liu, including two that gave him prominence almost equal to that of his nemesis, the late party Chairman Mao Tse-tung, have appeared at a new exhibit on the party's history in a museum alongside Tienanmen Square. Since Liu's purge in 1966 that began the tumultuous Cultural Revolution, he has been publicly reviled here as a "counterrevolutionary" and "renegade . . . swept into the garbage heap of history."

The pictures are perhaps the most startling of a series of hints of a new attitude toward Liu appearing in the official press in recent months. A complete rehabilitation of Liu, in the words of one diplomat, here, would be like the Americans rehabilitating Joe McCarthy." Although many of Liu's policies already have been revived, such as his emphasis on ability rather than political fervor in promotions, his full rehabilitation would probably speed implementation of those policies and lead to a return to influence for many more officials purged for following his line.

The case of Liu, who reportedly died in disgrace 10 years ago, still creates difficult problems for a ruling Politburo with many members previously on record as criticizing Liu. The complete signs of his return to favor indicate that the matter is under debate, and that some members of the leadership are arguing that some black marks on his record cannot be erased so easily.

Some diplomats suggested that a final report on Liu, whenever it is released, may praise his general record but still criticize him for some failings -- such as stubborness in going along with party policy shifts leading up to the Cultural Revolution.

Ironically, Chinese officials have in the last two years been suggesting a similar verdict on Mao -- that most of what he did was good, but that damaging excesses like the Cultural Revolution could not be overlooked.

The new exhibit, which opened yesterday to commemorate the 30th anniversary of the People's Republic, was hailed by the official New China News Agency for providing "a new evaluation of the role of leading figures who had made mistakes." The agency did not mention Liu but criticized former defense minister Lin Biao, who helped arrange Liu's purge, for distorting party history. In an apparent attempt to rule out any new distortions, the exhibit does include a small picture of Lin, who is mentioned as a war hero, in a group of other wartime party officers.

The exhibit at the Museum of Chinese History includes a large photograph of Liu addressing the 7th National Party Congress in 1945. Only four other leaders at that congress, Mao, Chu Teh, Chou En-lai and Jen Pi-shih are given similar prominence in that part of the exhibit.

A second photograph shows Liu at the second plenum of the 7th Party Congress in 1949. The exhibit ends with a huge painting of the ceremony on Oct. 1, 1949, in which Mao proclaimed the People's Republic from on the top of the Gate of Heavenly Peace -- the huge entrance to the Forbidden City where China's emperors lived. The painting shows Liu in the front rank of party leaders standing behind Mao, including Chou, who became premier, and Chu, the great Communist military hero.

Liu, born in 1898 not far from Mao's birthplace in Hunan Province, began his career in the 1920s as a labor organizer.He soon became the leading expert on the organization of the party itself. By the 1940s he was clearly number two to Mao, and remained that way until 1966, when he was serving as president, or what the Chinese called chairman of the People's Republic.

His texts on party theory and organization and the need for hard work and technical skill were required reading in China, but Mao began to suspect Liu's ideas would create a permanent elite divorced from the people.

Mao thus tried to destroy Liu's system in the mass purges of the late 1960s.

The chaos that resulted in the economy and society during the Cultural Revolution seemed to prove Liu right and Mao wrong. Mao allowed many of Liu's supporters back into power in the early 1970s. This process accelerated after Mao's death in 1976 and the second return to power of the Cultural Revolution's second most important victim, party Vice Chairman Deng Xiaoping.

Liu himself apparently did not live to appreciate his victory. Officials here privately confirm that he is dead, although they have provided no official account of the date or circumstances. A Hong Kong magazine with some unusual contacts here reported last year that Liu died in 1969 from pneumonia he caught while being transferred by train from Peking to new detention quarters in Henan.

In a two-hour speech Saturday, the man who now holds Liu's old position as official number two in the party -- aged military leader Ye Jianying -- appeared to compliment Liu without naming him. Liu presented the major political report of the 8th Party Congress in 1956. Ye, in his speech, lauded the "major documents" of that Congress, which he said "continue to be of great importance in guiding our work."

Ye disclosed that "at an appropriate time" the party Central Committee would hold a special meeting to sum up party history of the last 30 years, particularly the Cultural Revolution.Such a meeting would have to present a new verdict on Liu.