A wedding guest was left with a fractured skull and eye socket and three missing teeth after gatecrashers punched him to the floor at a reception.
Police are looking for the two men, one of whom was wearing a skull and cross bones t-shirt, after the attack on October 14.
The wedding crashers entered the reception in Clerkenwell, central London, uninvited and were asked to leave.
They refused and became abusive towards the wedding party including the best man and father of the bride.
As they were ejected they grabbed hold of one of the guests, punched him to the floor and stamped on his head before leaving.
One of the men is said to be around 6ft, black, slim and with long dreadlocks.
An image released from CCTV shows him wearing the pirate-themed top.
PC Ben Hurley, from City of London Police, said: “Violence of any kind will not be tolerated by the City of London Police and we would encourage anybody who recognises the man in the image released today to get in touch with us.
“This was a traumatic incident for the victim and numerous other people who had their special day ruined by violent strangers intent on causing trouble.
“It is vital we identify those responsible and bring them to justice.”
By Adela Whittingham