The photos were taken between 2001 and 2006. All of them predate the 2006 revision of the Army Field Manual, which strengthened protections for detainees and prohibited all physical force from being used in interrogations.
In other potential disclosures, the White House has until May 13 to decide whether to release a 2004 CIA inspector general's report on the agency's interrogation program or file a brief with a federal appeals court explaining why it refuses to do so.
As part of the same lawsuit, the ACLU is seeking to force the government to release cables and other documents describing the contents of interrogation videotapes that the CIA destroyed.
"The issue is a test of the administration," said Jameel Jaffer, director of the National Security Project at the ACLU. "We were gratified they released the memos last week, but it's clear there's still a great deal of information about the CIA's torture program and legal justifications offered for it that remain secret."
The White House appears to be feeling its way through the controversy, and even allies on Capitol Hill are trying to determine where the president stands when it comes to reckoning with the legacies of the Bush anti-terrorism strategies.
Although Obama and his chief of staff, Rahm Emanuel, made strong public statements that appeared to discourage investigations of the Bush administration, Obama this week told reporters that the Justice Department would decide if anyone should be prosecuted for violating legal bans on torture -- and he suggested that Congress might create an independent panel to review the past.
Rep. Jerrold Nadler (D-N.Y.), a liberal member of the House Judiciary Committee, said that Obama was showing a "laudable willingness" to listen to his critics on the left, and that White House officials had told him they were still examining their broad approach to national security.
"In the next few weeks we're going to know more about where they're going," said Nadler, chairman of a subcommittee on constitutional issues.
For the moment, the administration's signals on whether to investigate the Bush record are causing some confusion.
House Speaker Nancy Pelosi (D-San Francisco) assessed the president's position this way: "As far as I know, it has not been definitively stated as to what the policy is."
Peter Nicholas in the Washington bureau contributed to this report.