Updating my predictions/speculative list for what types Lunaala could be:
Updated list of type possibilities for Lunaala:
Fairy= For its magical associations to the moon
Ice = Refers to the lunar water ice on the moon, and ice's capability of reflecting light
Psychic = Used for cosmic/outer space references in general. (Lunar Dance, one of Cresselia's moves, is Psychic type, rather than Fairy type)
Flying = For the mere fact that Lunaala is flying.
Ghost = Refers to the aspects of the night, darkness, shadows, Lunaala's skeletal/creepy appearance, etc. (strongest possibility)
Dark = Refers loosely to the night, but is more associated with foul play, destructive urges, etc. (very unlikely, but still possible)
Water= The Moon is associated with water due to the fact it has the ability to control the tides and ebbs of the ocean via gravity.
Steel = May refer to Lunaala's scythe-like blade wing edges. Metals also reflect light, and Silver is commonly associated with the Crescent Moon.
8 possibilities in total if Lunaala ends up being a Mono Type, instead of Dual type.
Updated list of dual type possibilities for Lunaala:
Ghost type Combos:
Ghost/Ice, Ghost/Psychic, Ghost/Flying, Ghost/Fairy, Ghost/Dark, Ghost/Steel, Ghost/Water
Ice type Combos:
Ice/Fairy, Ice/Ghost, Ice/Psychic, Ice/Flying, Ice/Dark, Ice/Steel, Ice/Water
Fairy type Combos:
Fairy/Psychic, Fairy/Ghost, Fairy/Flying, Fairy/Ice, Fairy/Dark, Fairy/Steel, Fairy/Water
Psychic type Combos:
Psychic/Flying, Psychic/Ghost, Psychic/Fairy, Psychic/Ice, Psychic/Dark, Psychic/Steel, Psychic/Water
Flying Type Combos:
Flying/Ice, Flying/Ghost, Flying/Fairy, Flying/Psychic, Flying/Dark, Flying/Steel, Flying/Water
Dark type Combos:
Dark/Ghost, Dark/Ice, Dark/Fairy, Dark/Psychic, Dark/Flying, Dark/Steel, Dark/Water
Water type Combos:
Water/Ghost, Water/Ice, Water/Fairy, Water/Psychic, Water/Flying, Water/Dark, Water/Steel
Steel type Combos:
Steel/Ghost, Steel/Ice, Steel/Fairy, Steel/Psychic, Steel/Flying, Steel/Dark, Steel/Water
About 56 type combinations for Lunaala if it becomes a Dual Type. Take your pick, I'd say.
My personal picks for Lunaala's typing:
Steel/Flying, Ghost/Ice, Water/Steel, or Fairy/Ice
For Solgaleo, Fire is already pretty much given due to the sun being included and because of its signature move. May be mono type.
Secondary type possibilities for Solgaleo, if it ends up Dual Type:
Grass = May refer to the mane having a possible flowery/star shape. Tail may be a reference of a avocado done in half vertically.
Steel = Solgaleo looks rugged and tough, and futuristic. The sun has elements of iron in itself, but not a lot. The gold bits on its mane may reference to Steel.
Electric = The Sun has a natural electromagnetic field. Further, the gold parts on Solgaleo's mane may hint to Electric type.
Fighting = By far, the least speculated, but fits for Solgaleo's tough, strong look. May go well with the speculated Courage theme, a common lion association.
Psychic = For the fact that Psychic relates to cosmic concepts. Solgaleo's visor face and its fore-head mark make this type as likely possible.
Fairy = Solgaleo somewhat has a mystical look to it overall, and thus may connect to certain possible mythological tales involving lions, hence Fairy type.
To note and make clear, these are just speculations by now, and not considered fact. It includes speculations from both me and from other people.