Tallulah has a bit of a ridiculous ring to it. I haven't read the other responses yet, though I will, but I'm betting that most are saying it's a beautiful name and it's usable. But you'd have to consider that your child would be living amongst the general population and not amongst a small population of people who have more of an interest in and appreciation for names. I think the general population would look upon the name as being somewhat silly. I'm not saying that this view is correct, but I think that's what the general view is, and something like that has to be considered.
Celebrities can get away with certain names for their children that ordinary people can't. A celebrity's child will escape ridicule or teasing by virtue of the fact that he or she IS a celebrity's child. A celebrity will be looked upon as being so cool and avant-gard for using a particular name, but if an ordinary person uses it, people will just think, "They're nuts." Valerie Bertinelli and Eddie Van Halen named their son Wolfgang. That didn't lead to a big surge in the popularity of Wolfgang, but people realize that Wolfgang just isn't usable in English-speaking countries. Unless you're Valerie Bertinelli and Eddie Van Halen.
I don't see it becoming common.