On board facilities differ from freight vessel to vessel, and from ferry operator to ferry operator. There are 2 main classes of vessel -
Ro-Pax Ship
This is a vessel that is specifically designed to carry vehicles and passengers. On board facilities are usually very good. Generally speaking newer ships have better facilities. Modern vessels boast facilities including dedicated freight drivers rest areas, restaurants, bars, T.V. lounges, cinemas and shops.
Ro-Ro Freight Ship (12 pc ship)
This is a vessel designed to carry freight, but can carry up to 12 passengers. Facilities on board are basic and limited, usually a freight driver's rest area and basic cabins. However don't dismiss these services, as many operators have invested in providing top quality accommodation and services in the last 2-3 years. They are usually a little cheaper, and often provide a really good alternative to Ro-Pax routes.