You can appeal the rejected removal report in Wayspot Appeals
Murals are the one thing that do not have to be reported for removal. You can update the photo of the mural instead if they paint a new one. Everything else that has been replaced with something new has to be reported for removal and the new thing resubmitted if the new thing is eligible. The only way I can wrap my head around this distinction is that the wall is still the same wall, but Niantic has not explained it that way. Will try to find a link to that statement about the mural and edit it in.