I don't really have a real picture of the ithryn luin yet.
They are alatar and pallando or morinehtar and romestamo.
Alatar means radiant- one and morinehtar darkness- battler... He is a maia of oromes people, so he belongs to the same tribe as tilion does. I believe his names might tell us that he is a fighter and possibly a hunter and wanderer. I suggest he is a good horseman and archer too...
So i imagine him as a tall, strong and bright (radiant?) appearance.
Pallando means far- striding one and romestamo- east- helper. Or east-maker?tamo also means maker or smith)
So i guess he also is a wanderer and as a helper he might be a more nice and caring character.east- helper might suggest that his main area is the east, which doesn't has to be true for alatar who maybe does care more about the south or perhaps has no steady base at all.
Still he is also called a member of oromes people, unless we take a stronger empathy on the line that connects him with mandos instead
In the last case , if we'd interpret him as a member of mandos people he could be more connected to spirits, shadow, memory and death, the realms of his master. I suggest he might also be an advocate and seer.
I imagine him as smaller and more soft than the rather rough oremeian alatar, but maybe also as somewhat more dark and mysterious.