This post summarized the difficulties with the current tool pretty well:
The short version is that the limited hair and eyebrow options coupled with limited degrees of freedom on certain facial features like the nose and eyes currently make this task very difficult. I, myself, have tried to re-create celebrity characters from an existing show and ran into the same limitations. You’ll be able to get 70% of the likeness but the result just won’t resemble the original person enough to be recognizable.