How can I add an image / logo right above the grid?

How can I label a grid like the one attached

You could do that with a bit of custom CSS, like so:

table.form-matrix-table:before {
    background-image: url("http://www.corbanone.com/img/cos-logo.png");
    content: " ";
    display: block;
    height: 54px;
    margin-bottom: -20px;
    width: 217px;
}

Of course, you need to get permission from Corban OneSource to use their logo, but that would be the approximate steps that would need to be taken.

The CSS would be applied to all matrix fields in your jotform, so if you have 3 all 3 would have it, but it is easy to limit it to only one instead

You can see how to add it to your jotform here: Inject Custom CSS Codes