How short should I go?

I'm planning on having my hair  cut short, the question is, how short? I am  a 15 year old girl with an oval face and fine-ish straight hair.

Maybe this:
http://2.bp.blogspot.com/-lVOYeJS7P-g/TbUOYBOXghI/AAAAAAAAKyA/Pz7BenWnwEI/s1600/bob-haircut-with-bangs-Cute%2Band%2BCool%2BShort%2BHairstyles%2BFor%2BWomen7.jpg

Or something even shorter like this:
http://www.harpito.com/wp-content/uploads/2012/08/rihanna-pixie-cut.jpg

Or VERY short like this
http://www.stoltzimage.com/images/Emma-Watson.jpg

Or this:
http://www.beautifulhairstyles.com/2003/pictures/030909alyssamilano.jpg

Or partly shaved:
http://www.blogcdn.com/www.mydaily.co.uk/media/2011/02/ginnifer-final.jpg

What do you think I should do? I am considering going even shorter.

It is really hard to give suggestions on what cut you should do without seeing a picture of yourself first. All of them could work...or not work...depending on your hair texture, face shape, etc. If you give us a recent pic of yourself, then we could help with giving suggestions. Otherwise, we would just be voting on our favorite cut rather than voting on what would look best on you.