What exists in intergalactic space? Are there stars in these expanses?
Space is not empty, not even intergalactic space.
Space is not empty. It is not a complete vacuum. Even between stars and galaxies there exists gasses and dust. In intergalactic space the material will be very diffuse.
Also, in the emptiest space, virtual particle and antiparticle pairs form and annihilate each other.
Yes, there can be stars in intergalactic space. Stars can get ejected from galaxies by gravity of other stars. When galaxies collide some stars may end up in neither galaxy.