$base-path:'../images/';
$base-attr:'data-';

@function url($src, $path:''){
  @return unquote('url('+$base-path + $path+ $src +')');
}
@function url2($src, $path:''){
  @return unquote('url('+ $base-path + $path+ $src +')');
}
@function attr($arg1, $arg2:''){
  @return unquote('attr('+$base-attr + $arg1 + $arg2 +')');
}

div {
    background: url('image.png');
    background: url('image.png','img/');
    background: url2('image.png','img/');

  &:after {
    content: attr(value);
    content: attr(value, -extra);
    content: url('icon.png');
    content: url('icon.png','gfx/');
    content: url2('icon.png','gfx/');
  }
}