flag.css

#grey{
    background-image: url('https://upload.wikimedia.org/wikipedia/commons/1/1d/Marcus_Thames_Tigers_2007.jpg');
    background-size: cover;
    height: 252px;
    width: 480px;
}

#flag {
    position: absolute;
    z-index:3;
    left: 40px;
    width: 0;
    height: 81px;
    border: 38px solid #ef3e3e;
    border-top: 0 solid;
    border-bottom: 19px solid rgba(0,0,0,0);
}
#challenge{
    position:absolute;
    top:15px;
    left: -30px;
    z-index:3;
}

.challenge-overlay-image {
    background-color: rgba(0,0,0,0.35);
    z-index: 1;
    height: 252px;
    width: 480px;
    position: absolute;
}

.challenge-overlay-text{
    position:absolute;
    font-family:verdana;
    color: white;
    font-weight:bold;
    font-size: 30px;
    top: 50%;
    left:50%;
    z-index:4;
    transform: translate(-50%, -50%)
}

flag.html

<div id="grey">
    <div class="challenge-overlay-image"><div class="challenge-overlay-text">I disagree.</div></div>
    
    <div id="flag">
        <img id="challenge" src="http://s24.postimg.org/v9qcw9f9d/challenge.png" />
    </div>
</div>