Background Pattern To Your Blog

First you just create a pattern using phpotoshop or such softwares,then upload that image to your blog(create a new post and upload the image and save the post as draft)
then go to the html view of that post,coppy the address of the picture,it look like
http://bp1.blogger.com/images11.jpg

Then go to templates,edit the code inside body { }
body
{
background:url("http://bp1.blogger.com/mages11.jpg");
/*keep remaining same*/

}

instead of

background-color: #cccccc;

then save and publish