The betting company tweeted out photographs taken by a fan from the far left corner of the stand looking out towards the pitch.
It shows one of the goals being completely blocked out by the police control room, which sits at the corner between the Gorgie Road end and the new main stand.
Along with the images, Marathonbet tweeted: “A few snaps of Hearts’ new stands as it nears completion. It’s looking really good...”
Hearts have already informed supporters of the restricted view at the far end of the stand, saying they will not be offering tickets in that area unless there is significantly high demand for them.
There are plans to trim the size of the control room in the near future.
A statement from owner Ann Budge in October read: “The control room at the Gorgie end will have to be cut back to create a clear line of vision for supporters seated behind the structure.
“We will not be carrying out this work for the initial opening as we have scheduled this to be completed over the winter break.
“The seats with restricted view will either not be sold, or sold at reduced prices if demand exceeds supply.
“When the work is completed there will be a very small number of seats with slight sight restriction.”
It is understood Hearts have contacted Hibs to express their disappointment regarding the tweet.
Marathonbet have since deleted the post, which also included an offensive term in one of the pictures, from their official account.