ok, I don't know where my head was yesterday, must be exaustion from working with the kids at VBS at church. sigh...
This is quite easy and done with no plugins. Just add to the CSS inserts
HTML Code:
div.post.category-xxxxxxxx {background: options;}
for example, say you have the category 'recipies' and want the backgroound color to be blue you would use
HTML Code:
div.post.category-recipies {background-color: blue;}
and the background will be blue.
for an image you could use
HTML Code:
div.post.category-recipies {background-image: url('http://yourdomain.com/wp-content/uploads/2012/06/yourimage.jpg');}
you can also use the 'background' declarative to set multiple properties in one statement
remember that a post can be in multiple categories, so if you set this up for multiple categories you may not get the result you expect...