Most WordPress themes support to add a background image, you can add it in the customize area. The only problem is, that it will appear on every post or page.
How can you add background images on websites, to make it appear on just one post.
How To Make a Background Yourself
Background Images on Websites
At first you need a suitable picture. You can search for one on my other website, freeimages.siterubix.com. You can use one of my pictures for free. You can contact me in the comment area, and I will send you the original sized image by e-mail.
Make suitable image in Pixlr Express
My measure is 759px, that one is important, the length you can adjust to the post length. I have set it on 1550px
Write your post as usual
Add as last the html code into your editor
This is the code you need to paste.
Here comes your total post + images
Replace the http://html.your-background-image.jpg with your own http://
and change the values of the pixels into your own data.
Now go to Pixlr Express, choose for Collage and follow the instructions.
I hope you liked this tutorial, success with making your own background image behind your blog post!