I really love Welsh names, though I don't care much for the names you mentioned. I like
Morgan on a boy and
Morwenna is rather nice, though. Here are some of my faves:
GIRLS
Gwen - Not short for anything; I think it's spunky on its own.
ElenImogenNimueIsolde
BOYS
Ioan / Yoen - Yoen is how I'd spell it in English.
GarethGalahadCaedmonIdrisTristanSteffanCole - I suppose it's a Celtic name. Old
King Cole was a Celtic king, right?