Comment 2 for bug 901790

marlin at the opposite of nautilus respect your gtk theme.
So blame the theme ;)

For ambiance you can change the color in gtk-3.0/gtk-widgets.css.
You ll find a line with GtkIconView.view.cell (line +/- 800)

just comment the section replace with this:

.view {
        background-color: @base_color;
}

.view:selected {
        background-color: @selected_bg_color
}

and u ll got a nice orange background. I am no expert in theming so i can't really say more.