Melbourne journalist and former Pirate Party Australia staffer Asher Wolf posted the photos on Twitter on Wednesday evening, after allegedly finding them on an open Facebook group.
The veracity of the images has not yet been confirmed by the Immigration Department or officials at the centre.
The images show a number of apparent asylum seekers, some heavily bruised or bearing stitches and bandages.
Another shows two men posing with their IDs in front of poster bearing an image of Reza Barati, the detainee killed during the recent riot at the centre, and the words “we never forget”.
Other images show what is believed to be blood stained bedding, a blood trail on a set of lockers and bullet holes.
Wolf stated that the bullet holes depicted were at head height.
The images follow fresh claims of self-harm and bullying at the detention centre, aired by SBS on Tuesday.
Exclusive footage obtained by Dateline details a string of allegations, including incidents of racism and bullying of detainees by guards on Nauru and Manus Island centres.
A former Salvation Army worker reported men self-harming on an almost daily basis while at Nauru.
The university student, identified as Marie, said she had witnessed asylum seekers cutting their wrists and necks, trying to suffocate themselves with plastic bags and stitching their lips together.
The former worker also detailed widespread bullying by the guards, including an incident where several ex-Army officers would mime shooting detainees while on site.