a few idea-rs
You could add a form of inactive ember stone to the game environment (not a harvested crafting or otherwise usable resource) that absorbs sunlight in the daytime and releases it at night, a non-destructible environment enhancer. Add them to the game world like trees or have trees sprouting out of some of them and the entire tree glows faintly.
Something to do with lore and the main 'ember' theme of the game + work toward solving the problem of difficult night-time navigation. Certain points of interest could contain a higher density and/or variety of these enhancements to grab players' attention to the area as well as facilitate night-time combat.
I like that guarded roads have the lanterns hanging along them. Maybe there could be a few watchtowers with signal fires lit on top of them for night time navigation or ground-level guard camps with a bonfire. Each one could have a sort of framework structure around in varying shapes, animals, or other symbols to help the player identify where they are or at least which one they are looking at as opposed to them all looking the same.
Fireflies are also great, perhaps a smaller version of them that is non-combat/inactive and roams around at night illuminating tiny areas around them. Swarms of them hovering half a meter above ground level would be effective but may cause a performance hit.
There could be various regionally based sources of light in addition to reducing the overall darkness in most places while intentionally leaving some areas quite dark.
Who says we are limited to only one moon and sun? Maybe there is an ember-star that is visible from one side of the planet at 'night' that isn't nearly as luminous as the 'day' star. Hard to say without knowing the physics of the world we play on
Enchanted/special materials crafted helmet, necklace, other equipment items intended to provide a hands-free glow or forward light source for the player.
I suppose you could make some of these resources harvestable and only at night, that would actually be interesting. You already have the tech for adjusting spawn tables of mobs based on time, so how about resources? Could make it so they are only visible or spawn at night.
I mentioned elsewhere the idea of an adventuring/survivalist profession which would include camping, perhaps higher tiers of the skill offer more amenities around camp, one of which would be a larger fire providing more light to the surrounding area (and a faster recovery rate of battle fatigue, hp/stam, more crafting options, repair, etc). I think having such a profession and more total trade skills while holding the character limit per account constant would go a long way toward combatting 'one player does allts' when it comes to professions (one player doing every skill across a number of alt characters). Naturally this profession would pair well with forestry!
Variety and unique biomes are fun.