Before you start,

I am not responsible for anything that happens to your space when you try out this tutorial. If done incorrectly, it may spoil your space. Delete the blog entry you created doing this tutorial to revert your space to normal if anything goes wrong

• First get the URL of the image you want to use as a background in the blog entries that are present on the front page of your space.
• Click here to learn how to upload an image and get its URL.
• Create a new Blog entry. [Click on  'add entry' in your blog module]
• This Blog entry will be a dummy as all the blog entries below this get the background you want. So try not putting anything in this blog entry.
• Click on the   button present in the blog editing tools.
• And enter the Following code :

<pre></table></table><table background="URL OF BACKGROUND IMAGE" height="xxx" width="xxx"><tr><td><div><table style="display:none"></pre>

• Replace the URL OF BACKGROUND IMAGE with a URL a picture. [see step 2]
• Replace the xxx with numbers to determine the picture size.

For e.g. :

<pre></table></table><table background="http://img401.imageshack.us/img401/3285/back1aw.gif" height="xxx" width="xxx><tr><td><div><table style="display:none"></pre>

• Press the 'Publish Entry' Button to publish your blog entry.
• Preview your space to see the final effect.

Note :-

• If you do not like it, Try getting pictures with the same width [in px] as your blog entries.
• Delete this blog entry if you feel that it has spoiled your space somehow.
• If you decide to add more entries above this dummy blog entry, you will notice that the background does not come onto them. 
• Delete this dummy blog entry and repeat the above steps again, so that it is placed above all your blog entries and that all entries below this dummy one get the background picture effect.