Vanaheim is a world for which we have no sources at all that tell us anything about how people imagined the realm to look like. The Edda’s mention that in the early days of the Universe there was a war between the tribe of the Aesir and the tribe of the Vanir, which neither side could win so they made peace. In order to secure that peace, both sides exchanged hostages. The Vanir sent Njörd, Frey and Freya to live with the Aesir in Asgard and by the many stories we have about them we can make some educated guesses about what Vanaheim might have looked like in the minds of the people that practiced the Norse system in the days of old.
Njörd is associated with the ocean and according to Snorri was able to still the sea, grant you success when hunting and fishing and was generally thought to be able to bestow wealth upon those who asked him for it. Frey is said to rule over rain and sunshine, therefore being able to grant fruitful fields as well as well as numerous and healthy offspring while his sister Freya is related to love and sex. Something that is often ignored in regards to Freya is her close connection to war and death. While Odin receives half of the dead after battle, the other half goes to Freya and there are several stories about her which clearly show her warlike nature and short temper.
So the Vanir Gods are presiding over things like wind, rain, sunshine, procreation and death and while assigning limited functions to the different Gods is generally not a good idea we can still see that all the functions they are associated with relate to natural cycles. At the same time, they are described as being very regal. The names of Frey and Freya are actually no names at all but titles, meaning as much as “The Lord” and “The Lady”. Frey is even the mythological founder of the Ynglings, the oldest royal line in Sweden.
Since there are no sources that describe the realm of the Vanir Gods, we can only speculate as to what a Scandinavian living in the 8th or 9th century would have imagined when hearing the word Vanaheim. Based on the function and character of the three Vanir Gods that we actually know about it is probable that their world is a majestic yet wild place where game, fish, vegetables, fruits, nuts and berries are always plentiful. Freya’s characteristics suggest that it isn’t a place where all creatures live in harmony though. Since it is a godly realm plants would surely find perfect conditions and grown exceptionally well and fast but the same would have to be assumed for the animals that feed on them. If the herbivores thrive so do the carnivores and so this realm was probably seen as a place of exceptional growth, thriving with life in all its forms but also as a battleground where all kinds of organisms would confront each other in order to create ever healthier and stronger lifeforms.
We do not know if some people were thought to go to Vanaheim after their death as it isn’t mentioned anywhere. What we do know is that the Vanir have a close connection to seafaring and ships. Njörd’s realm is called “Noatun” which means “ship-enlosure” or “harbor”. Frey owns the best of ships called Skidbladnir that always has favorable wind and can be folded up to fit inside his pocket whenever he doesn’t need it and Freya’s hall in Asgard is called “Sessrumnir” which is also the name of a ship in one of the ship-lists presented in Skaldskaparmal. What we also know is that Archeologists have unearthed many ship burials in Scandinavia and the British Isles as well as burials that were covered with stones arranged in the form of a ship. Maybe people buried in these kinds of graves were destined for an afterlife in Vanaheim but since we have no written sources to confirm this, this remains only a theory.