You'll get best results with my backgrounds if you also use the Minima template from Blogger:
Now that Blogger has brought in it's "New & Improved" design editor, it's a bit more involved to choose to use one of the older templates like Minima.
1. Go to the "Design" page in your Blogger Dashboard
2. Click on "Edit HTML"
3. Scroll to the bottom of the page and click on "Select Layout Templates"
4. Choose Minima and click the SAVE TEMPLATE button.
To install the code for the background you've fallen in love with:
1. Go to the "Page Elements" section of "Layout"
2. Choose "Add a Gadget"
3. Select "HTML/Java Script"
4. Paste the background code into the Content section and save.
Can't find the code you need?
The code for each background is shown below the backgrounds' thumbnail in each post.
Just highlight it and press Ctrl+C to copy.
Try checking out the FAQ, or email me if the answer's not there.