The group broke into carriages on one of the railways 1930s Gresly Teak Set trains stationed at Pickering station on July 23 last year.
Every light fitting was smashed, mirrors were broken, furniture ripped and wooden panels damaged.
Food and wine stolen from the train was also eaten and drunk by the group and thrown over the carriages.
The damage was discovered by a member of rail staff and has cost more than Â£27,000 to repair.
British Transport Police begun an investigation and CCTV footage from a level crossing nearby captured the group in the area at the time of the incident.
They were spoken to and charged with theft and criminal damage.
All eight teenagers pleaded guilty.
On March 13 at Scarborough Magistrates’ Court, a 17-year-old boy from Pickering, who cannot be named because of his age, was ordered to pay compensation of Â£530 and will have to complete a twelve-month youth offending panel contract.
The same day, two 17-year-old boys from Pickering were sentenced to a youth offending panel contract for six months and will have to pay fines and costs totalling Â£135 each.
On March 27, magistrates at the same court ordered a 17-year-old girl from Pickering and a 17-year-old boy from Ampleforth, who cannot be named, to pay compensation of Â£535 and will have to complete a twelve-month youth offending panel contract.
On April 10, a 17-year-old male from Malton was ordered to pay compensation of Â£535 and will have to complete a twelve month youth offending panel contract.
On April 26, magistrates at the court sentenced Mollie Dawson, 18, of Keld Head Orchard in Kirbymoorside, to a twelve-month conditional discharge. She was ordered to pay fines and costs of Â£635, including compensation of Â£530.
On the same day, Benjamin Terry, aged 19, of Jute Road in York, was sentenced to a twelve-month conditional discharge and ordered to pay fines and costs totalling Â£135, including Â£30 in compensation. Sergeant Nigel Ashworth, of British Transport Police, said: “The NYMR is a charitable trust which relies solely upon donations and hard work by volunteers.
"Seven carriages in total were damaged by the atrocious behaviour of this group, every light fitting was smashed, furniture ripped and windows broken.
"The repair bill totalled over Â£27,000. In addition to the financial outlay, it must have also been heartbreaking for all those who had invested a considerable amount of time and hard work to see it destroyed in this way by these mindless vandals. Each carriage had taken a minimum of two years to restore by volunteers; one carriage in particular took over 22 years.”