Cheryl, who has been rumoured to be making a return to the show, remained coy about her reason for sharing the photo, simply accompanying it with the hashtag "Tbt". But it has fuelled speculation that Simon has convinced her to come back on board the ITV show.
It comes after Nicole Scherzinger confirmed that she has decided not to return for the next series. The former Pussycat Doll instead wants to focus on her own music, and is said to be "heartbroken" after spending months "agonising" over the difficult decision. Gary Barlow announced he would be leaving the show last year.
Music mogul Simon, who famously axed Cheryl from the US version of the X Factor in 2011, is said to have wooed her back with a butler service dinner at the weekend.
"It was just him and Cheryl," an insider told the Sun. "Simon was offering an olive branch. It was a very civil evening.
"She was happy and loved talking about the show. It's pretty much nailed on that she'll be back."
Just last week, Simon, 54, confirmed that he would be returning for the 11th series of the UK talent show – but has yet to announce who will be joining him on the judging panel.
Now, though, an announcement confirming Cheryl's place seems imminent.
By way of incentive, Simon is said to have offered the Newcastle-born brunette a £2million pay packet, as well a free-reign to verbally abuse him.
"Simon is ready for the fury of Cheryl onscreen," a source told the Daily Star. "He has hade it clear she can say what she wants to him, and get the fans booing and hissing him at any stage.
"Obviously fireworks on-screen between the pair could make for astonishing viewing and Simon knows that."
Simon, who fired Cheryl from the US version because viewers couldn't understand her Geordie accent, said he was thrilled to be returning to the show.
"It's been three years since I last judged the competition and I'm excited to find a global superstar again," commented to star, who is expecting his first child with socialite Lauren Silverman.
"Despite all the rumours, ITV and the producers have not decided on the rest of the judging panel quite yet. You'll just have to wait and see."