First, in order to be able to post any sort of images, even smilies on you page, your account has to be confirmed. If it isn't confirmed, you can't even post a background on you page.
Second, it depends on how much you want to complicate yourself with codes and stuff. My page as an example: I don't have a background, I only posted images and texts, using the Insert/edit image button.
http://us.ohmydollz.com/board/viewtopic.php?id=575
Though be careful with what coding you use, the ones on the forums are recommended, because other forms of codings may mess up your page completely, going so far as disabling your save button, you comments page and stuff like that.

This happens to me but I figure it out within an hour or two. I cannot answer why it happens but it just happens for a reason.
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Do not place the image first! Type in a word, letter, symbol etc before you post the photo. Then once you've done that, post the image in front of the first letter you made. Then you can do whatever you want with it.