Anything with two syllables or more that has silent letters.
Vivien - K, Vivienne - a bit frilly
Isabelle, Annabelle - both frilly
Names that have an ee sound in, or seem just a pile of vowels.
Ameeeeelia
Aureeeeelia
Elodie
Ottilie
Names that are OK but are spoilt by adding another syllable to.
Julia - fine, Juliana - frilly
Lilian - fine, Liliana - frilly
Georgina - fine, Georgiana - frilly