The facilities offered on-board each cargo ship varies, but there are some standard features.
Luggage
Passengers luggage should be able to fit within the confines of their cabin. Some ships also have a weight limit for passenger baggage.
Entertainment
Most cargo ships have a passenger lounge, normally situated next to the dining area. Lounges normally contain a television with VHS/DVD player, as well as a selection of games, books etc. The majority of entertainment materials are likely to be in the language of the ship's crew, so you may want to bring some of your own.
Food & Drink
In some cases, the Lounge area includes a bar serving drinks. Alternatively, passengers may be permitted to use an Officers' bar. The selection of drinks tends not to be that extensive, but the prices are favourable as they are duty-free and usually not-for-profit. Generally speaking, only cash is accepted on-board, and Euros are prefereable.
Meals are generally taken with the crew and sometimes the Captailn in the Officers' Restaurant. Passengers will generally have their own table. Food tends to be served a little earlier than usual (e.g. breakfast 07.00-08.30, lunch 11.30-12.30, dinner 17.00-18.00). Don't expect the food to be gourmet-standard, but do expect it to follow the nationality of the ship/cook. There isn't a lot of choice on-board, so you may have to eat outside your comfort zone. Snacks tend to be available outside of meal times.
Exercise
Some ships have an indoor swimming pool on-board, and occasionally even a sauna. Exercise equipment may also be available (although shared with the crew). This may include items such as exercise bikes and rowing machines.
Laundry
Bed linen and towels are changed on a regular basis, but passengers may also use the on-board launderette (where available - shared with crew) for personal items.
Email / Telephones
Ships tend not to offer passengers access to telephones or internet, as this is expensive. Passengers are encouraged to post letters to family and friends from ports. Postal addresses may also be given out in advance so that correspondance can be sent to you at port.
Disabled Passengers
Cargo ships are not designed to carry disabled passengers, oweing to the number of stairs involved. As a result, passengers with physical disabilities or mobility problems are not able to travel.
Travelling with Pets
Unfortunately, no animals of any sort are permitted to be transported on-board.