html:after {
    content: "";
    background-image:
        url(../img/battle2.png), url(../img/battle3.png), url(../img/discovery2.png), url(../img/discovery3.png), url(../img/action2.png), url(../img/action3.png), url(../img/negotiate2.png), url(../img/negotiate3.png), url(../img/knowledge2.png), url(../img/knowledge3.png)
}