The pictures, which police said Holmes took of himself with an iPhone before the shooting rampage at a midnight showing of a "Batman" film last summer, capped three days of hearings in which prosecutors laid out their case for putting him on trial.
The former neuroscience doctoral student is charged with multiple counts of first-degree murder and attempted murder for the 12 people who were slain and dozens of others wounded at the opening of "The Dark Knight Rises" in the Denver suburb of Aurora.
Prosecutor Karen Pearson said in her closing arguments that Holmes would have killed more people had his rifle not jammed, adding, "He certainly had the ammo to do so."
The July 20 attack marked one of the most lethal mass shootings in US history, and ranked as the deadliest of 2012 - a year notable for rampant gun violence - until 20 children and six adults were killed last month at an elementary school in Newtown, Connecticut.
Wrapping up the prosecution's case against Holmes on Wednesday, Aurora police Sergeant Matthew Fyles ran through pictures Holmes took roughly six hours before the deadly assault on the Century 16 multiplex near his home.
In one picture, Holmes grinned while holding the muzzle of a handgun near his face. He stuck out his tongue in another photo.
His brightly dyed red hair was visible in both pictures, and he wore black contact lenses that made his pupils appear abnormally large. In another picture taken the same evening, his bed was strewn with guns, ammunition magazines, body armor, a gas mask and other gear.
Holmes, in a self-portrait taken on July 5, posed with a semi-automatic rifle and wore the tactical body armor he was wearing when he was arrested.
A separate photo taken on July 16 showed the booby-trapped explosives Holmes is accused of rigging up inside his apartment, which according to police he had intended as a diversion to draw authorities away from the theater on the night of the assault.
The explosives were safely dismantled after the shooting.
Holmes' lawyers, seen by legal experts as preparing for an insanity defence, had been planning to call two witnesses to testify this week about their client's state of mind around the time of the shootings.
But in a surprise twist after the prosecution rested its case on Wednesday, public defender Daniel King said his team had decided not to present its own evidence or testimony.
"This is a preliminary hearing and not the proper venue or time to put on a show or truncated defense," King said. The defence also declined to make a closing statement before the hearing was adjourned.
Arapahoe County District Judge William Sylvester said he was taking evidence presented this week under advisement and scheduled a new hearing for Friday that he said would serve as a "status hearing and/or arraignment."
If the judge orders the case to proceed to trial, Holmes is widely expected to enter a plea of not guilty by reason of insanity. Authorities have offered no motive for the slayings.
Holmes' lawyers have said he suffers from an unspecified mental illness, and went out of their way in cross-examining prosecution witnesses to highlight strange behavior he exhibited before and after his arrest.
Homicide detective Craig Appel acknowledged under defence questioning that Holmes, 25, tried to insert a staple he found on a desktop into an electrical outlet while being interrogated at police headquarters.
During that interview, in which Holmes had plastic bags placed over his hands to preserve any traces of gunpowder residue, Holmes also gestured with one of the bags as if it were a talking hand puppet, Appel testified.
One moviegoer who survived the shooting with a bullet wound to his head, Yousef Gharbi, 17, told Reuters after attending Wednesday's hearing that the photos of Holmes displayed in court made a strong impression on him.
"I had it in the back of my mind he might be insane," Gharbi said. But after seeing the self-portraits, he said Holmes "looked like he was having a great time."
Police testified that Holmes, who bought his movie ticket 12 days in advance, left the screening minutes after it began and re-entered Theater 9 a short time later and lobbed a tear-gas cannister into the auditorium.
Armed with a semi-automatic rifle, shotgun and pistol, police say, he then sprayed the audience with bullets. He surrendered to police in the parking lot minutes later.
On Tuesday, a detective played recordings of two emergency calls placed from inside the theater during and after the shooting. A burst of 30 gunshots was audible in one 27-second tape.
In another, a 13-year-old girl caught in the shooting with her 6-year-old cousin, Veronica Moser-Sullivan - the youngest person to die - and Veronica's pregnant mother, Ashley Moser, who was badly wounded, was heard frantically pleading for help.