A lararium could be a wall-cupboard with doors, an open niche with small-scale statuary, a projecting tile, a small freestanding shrine, or simply the painted image of a shrine; most Romans lived in apartment blocks or small-scale rural houses, with minimal indoor facilities.
Lararia usually held images of one or more bearded or crested snakes, which are presumed to represent the family genius, fertility, or generative or procreative power.
Lararia almost always contain the central painted image of a togate man, head covered by a fold of his toga, as if at worship or fulfilling his domestic priestly duties, carrying or offering a patera, or sacrificial vessel.
The Lar Familiaris is a more-or-less standard image, like other lares he is young, slender, clad in high boots, a short tunic, and a hitched undergarment.
The Lar Familiaris, on the other hand, protected all household members, free or slave, and was associated with a particular place.
Tradition holds that a family's Lar would generously help those who honored him by devotionals and sacrifices, but would turn his back to those who would not offer him thanks or neglected him.