Where can we park/sleep overnight?
New laws prevent "wild camping" in a camper in Iceland. As you drive around the island, you'll find amazing campsites everywhere with good facilities. Now that the infrastructure is more developed we recommend taking advantage of it. If you don't, you will become hugely unpopular with the locals and the police will stop you and fine you.
When it comes to the winter months, things aren't quite as ironed out and we recommend you read through the Winter Camping section for any camper trip outside of May-September. There you will find a list of open campsites, hotels, and hostels that allow camping on their grounds and more detailed information.