Add image to textfield – DSMGuestbook

Hi! I was wondering if someone could help me out with a image issue with the DSMGuestbook. I will have a background image in the text fields if you understand what I mean. When I try to add a backgound image the css code background-image: url(‘img/image_url.jpg’) turns into background-image: url(\\img/image_url.jpg\\), and the image doesn’t appear. What am I doing wrong? And a last question: How can I make the messages be like the comments in wp (the first comment has coloured background, the other is white, the third has coloured background etc…)

Thanks!