If I were you, I would choose a subject that you have worked on it for a long time (expert by direct experience) and after finding the best script of this kind develloped by someone that you respect, try to modify it and improve it.
That is an active way of developing skills and style.
You won't like to change the author's style. And since the concept comes from another mind you are going to be forced to understand the way of thinking of this author.
That is a universe to disconver for your improving. And it is free. Just try to improve the code and then publish it, mentioning the improvements and the original author.
Finally, if you didn't learn a lot by re-writing the code you are going to learn a lot by the critics or by the people that love your improvements :)