I only found one instance of the lantern's use in 2fort (above the crates in Red's base near the sewer stairway) and it had no sprite or anything near it. Maybe I'm missing something obvious but I think it may be part of the model, or maybe the model calls some particle effect you can find on its own elsewhere.
The lantern's skin comes in two versions, "on" and "off" so aside from the difference in glass, you may find something else in those textures too.