Though there are lots of peaceful melodies which can serve as lullabies, I always think of them as songs with lyrics
Here are some of my favorites
Scottish
Chro Callain
Hovan Hovan (I left my baby lying here)
Scots Cradle song (balloo, balloo my wee wee thing)
Hushabye Bairnie
Bonnie at Morn
Dance to your Daddy
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"Celtic"
Gartan Mother's Lullaby
Hear the wind blow
Wexford Lullaby (John Renbourn)
Sweet and Low(wind of the western sea)
White wings (they never grow weary)
All through the night
All the pretty horses
Suo Gan
The Fairy tale lullaby (John Martyn)
Isle au haut Lullaby (Gordon Bok)