The images, which feature the 21-year-old posing for photos in United's home jersey and signing his Old Trafford contract with his entourage, went viral on Twitter after the leak.
It's claimed the pictures were taken when Wan-Bissaka visited United's Carrington training complex on Thursday to put the finishing touches on a six-year deal that is expected to be unveiled on Friday.
The transfer fee to be received by Palace will make Wan-Bissaka the most expensive full-back in football history with the England Under-21 defender likely to arrive as the club's first-choice right-back.
First glimpse of Aaron Bissaka in the new United kit! pic.twitter.com/p1uV34WzGD— The Man Utd Way (@TheManUtdWay) June 27, 2019
Wan-Bissaka won Palace's player of the year award last season despite having only made 46 senior appearances for the club since coming through their youth academy and making his senior debut in February 2018.
United legend Andy Cole believes the acquisition of Wan-Bissaka would represent a coup for boss Ole Gunnar Solskjaer with the player's rapid development a sign of his potential.
"I believe [it is good business]," Cole told Sky Sports .
"He’s a very good young player. He’s done very well considering he didn’t start his career as a full-back. He’s done extremely well playing there.
"If you come to a club like Manchester United, no doubt he will learn a lot more and have the opportunity to play at a level that he would no doubt like to play at."
Wan-Bissaka, who is not yet a full England international, started the first match in the Three Lions' Under-21 European Championship finals campaign, scoring an unfortunate 95th minute own goal that handed victory to France.
England Under-21 coach Aidy Boothroyd dropped the London-born youngster for the remaining two group matches prior to his side's exit, insisting that the player was distracted by his impending United move.
"When that speculation is flying around it is bound to turn your head," Boothroyd said after the France defeat.
"For a young player who all he knows is Crystal Palace academy, Crystal Palace first team it would be daft not to say that in some way he must think about it."