[ozzy47]

Ok I found a way to do it, in your style open your CSS templates, then find editor.css.

Find this bit of code:

.texteditor.forum .cke_skin_kama textarea.cke_source,
.texteditor.forum textarea {
    color: {vb:stylevar editor_text_color};
    font: {vb:stylevar postbit_font};
    white-space:pre-wrap;
    background: {vb:stylevar editor_background};
}

Replace it with this:

.texteditor.forum .cke_skin_kama textarea.cke_source,
.texteditor.forum textarea {
    color: {vb:stylevar editor_text_color};
    font: {vb:stylevar postbit_font};
    white-space:pre-wrap;
    background-color: {vb:stylevar editor_background};
    background: url(images/chain_gradient.jpg); no-repeat;
}

Of course change chain_gradient.jpg to your image that you want to use. And load your image that you want to use to your images folder.