The family of an Iraq war veteran murdered by her boyfriend are devastated after her headstone was deemed inappropriate by cemetery staff and removed.

Army Sergeant Kimberly Walker's family say they had prior approval from Cincinnati's Spring Grove Cemetery to mark her grave with two headstones shaped in the likeness of her favorite cartoon character, Spongebob Squarepants. The 7-foot-tall stones honored both Walker and her surviving twin sister. Walker was a huge fan of the cartoon, her family says, and she was even buried with a Spongebob pillow in her casket.

The Walkers received a call the day after the installation of the monuments informing them that they would have to be removed. According to the cemetery's president, Gary Freytag, the monuments are not appropriate for the historic burial site.

"The family chose a design with the guidance of a Spring Grove employee who unfortunately made an error in judgment," he told CNN. "The monument does not fit within Spring Grove Cemetery guidelines, was not approved by senior management and cannot remain here."

Freytag said his staff will work with the Walkers to decide on a more traditional gravestone bearing the likeness of Spongebob.

"I feel terrible that it got to this point but I'm hoping we can come out at the other end of the tunnel with a solution," he said.

But Walker's family are not satisfied.

My sister served our country and most people try to accommodate veterans and try to take care of them," said Walker's sister,  Kara, an information technician with the U.S. Navy. "For them not to accommodate and respect what my sister sacrificed, not only for my family, but for everyone else in this country, really bothers me."

She feels the only solution is to honor the family's decision and restore the headstone.

"They already brought enough grief and pain to the family," she said. "We want what we paid for and what I know my sister would have wanted."

Walker served two tours in Iraq in 2006 and 2010, assigned to the 2nd General Support Aviation Battalion. She was found beaten to death in a Colorado Springs hotel room on February 14 of this year. Her boyfriend, an Army sergeant stationed nearby, was arrested and charged in the crime.