It's always a good practice to ask for permission if you want to use any elements from another theme. Many of them are generous in heart and will grant you to permission to do so.
To help you with theming, there is a collection of tutorials for Sony Ericsson theming
. There you will find links, template, tutorials to create basic to advance theming elements. With practice, I'm sure you're able to create elements that not only impressive but such that other people will want to use them for their themes instead. A good place to ask question, collect feedback & improve your skills is the ThemeMaking Challenge
. Don't be afraid when you see so many quality themes there. All those themers start from somewhere then improve as they practise.
We'd give MaWaHe a chance. Try not to jump on everybody who uses other people's elements. People become defensive the moment we say they are thief. Feel like sharing a story I read sometime ago. An old man was sitting in a coffee shop with his mobile phone on the table. He was reading newspaper. Suddenly, he heard a loud bang & turn his head. A second later, his phone is gone. He saw a young lad who was sitting nearby on his way out of the shop. He stopped the lad & ask him if he saw his phone. The lad said no. The old man then asked him to help find his phone because it's difficult for him to bend down for long time. Guess what happen? The lad "found" the old man's phone and return to him. Had he shouted at the lad & say "you thief, give me back my phone!", will he got back his phone? Your call.