Well here's an idea.   A tattoo artist by the name of Peter Van Der Helm plans to offer a service to people who want to preserve their tattoos forever.  Here is a video of Peter creating a tattoo for one of his clients of his 'Walls And Skin' parlor.

Here is a photo of the feature the Walls And Skin Parlor is offering.  Click on the photo to visit their website.

Walls And Skin

According to an article in the Chicago Tribune, which you can read by clicking here, when the person with the tattoo to be preserved dies, a Dutch pathologist will remove the tattoo and freeze or package it in formaldehyde, preferably within 48 hours. It will then undergo a 12-week procedure of water extraction and will be replaced with silicone, leaving a rubbery substance.