Our very own Lance Willett spoke recently at WordCamp Phoenix about the art of finding the perfect theme:
Feel free to get started by checking out our latest four themes that were added to the WordPress.org theme repository: Forever, Vertigo, Reddle, and Quintus!
ThemeShaper 
On the topic of themes and customising, I have a question.
If one takes a theme as a starting point, say Twenty Twelve for example, and starts to modify and customise it, at what point could that person rename it and call it their own?
This is a somewhat subjective issue, so how about: When you feel it’s uniquely yours.
The WordPress Theme Review Team looks for “significant differences” to the original, to determine the uniqueness of a theme in its review process. I think this is a good general rule of thumb.
Thank you for your response. I’m assuming that “significant differences” would mean more than just a different style.css, but differences across all of the pages.
Also I’m really enjoying this site and the articles that are on here. I really enjoyed the “The ThemeShaper WordPress Theme Tutorial: 2nd Edition” by Ian Stewart. I was wondering if any one has thought a bout doing a more advanced tutorial that looks more advance parts of theme building i.e. creating a custom “theme options” page, add social media support, and other tips and techniques that are commonly used.
I see the clear voice here but not for the slide. Some time it to small and far in this video. So, I can read it.
Is there possible to share the presentation slide online?
Thank you very much.
-Pernando
Of course Pernando, you can find the slides and many more information and resources at themeshaper.com/jumpstart.