use the [img] tag and put the url of the picture in between it.
for example
[img]www.thesiteurl.com/picture1.jpg[/img*]
without the * symbol, this allows pictures to display on forums, in terms of the background, there was a option to put a picture as the background image, which i just put the direct link of the picture, which wouldbe like
www.emopics.com/pictures/picture4.jpg
notice at the end it has ".jpg"
u can right click a image and check the url of it in teh view picture thing when u right click the pic, the url of the pic should be at the top