A holo-image was a holographic reproduction of a three-dimensional scene or object, similarly to a photograph, that could be created with a holographic imager.
Talaxian technology included the ability to generate holo-images, however, if not properly maintained, they could fade over time.
Neelix lost his entire family to the metreon cascade. When Neelix was delivering "a treasure trove" of Hansen field logs to Seven of Nine in 2375, he lamented that all he had left of his family was a faded holo-image of his sister Alixia. (VOY: "Dark Frontier")