I'm not precious about the gender of our bank note faces but I do think it's important to have some female representation on stuff like that. There aren't enough female role models in the public eye for young girls to look up to IMHO, they're usually either prancing around on TV half dressed, in lads mags undressed or in the tabloids getting slated for being too fat/thin. I think it's important, particularly young, girls can see women who made it into the public eye for something not body image related.
As for the people who tweet rape threats, it's good that Twitter and FB allow these people to be so easy to identify, most of the clowns won't even bother having fake accounts or masking IP addresses, so even our Police should be able to find them. There's plenty of laws in place already to punish these people if the Police can be bothered. In my experience it's only people with no argument that resort to abuse and threats, their fists work faster than their brains.
As for freedom of speech, Facebook and Twitter are not platforms for free speech. As with most platforms (like forums) they have terms of use and you agree to abide by them when you sign up. Tweeting rape threats is not a freedom of speech issue. If you want to exercise your freedom of speech then host and develop your own website and put it on there and you can say whatever you want, but no one will hear you.