It would be cute for a pet but I don't really care for it as a person's name. I do like
Hadley and Arley for a girl though. I prefer
Harley over
Hartley, but I don't care for motorcycles and it seems like
Harley would always be associated with Harley-Davidson.
Hartley would be ok as a middle name.
Arielle and
Katerina are both very pretty.
Arielle Hartley and
Katerina Hartley sound better to me.
Hartley Arielle and
Hartley Katerina reminds of the format of names on class lists where the last name is mentioned first (ex. Smith,
John).