All these backgrounds are suitable for Blogger MINIMA template.
Now I’ll tell you how to change your background to Minima.
Don’t worry, it’s very easy!
1. Go to your “Design” page. Make sure you’re sign in to your blogger account (image below). Choose "Edit HTML".
2. Scroll down and choose “Select Layout Template”.
3. Then choose the first template “Minima”. Then “SAVE TEMPLATE”.
Now you have Minima template in your blog, isn’t it easy! Please, just ask if you have some problems. I try to reply as soon as possible.
And here’s instructions how to add background and header.