Оформление checkbox'а внутри label

 
.demo2 {
    user-select: none;
    position: relative;
    cursor: pointer;
}

.demo2 .checkbox__input {
    appearance: none;

}

.demo2 .checkbox__input::before {
    content: '';
    display: inline-block;
    margin-right: 13px;
    width: 13px;
    height: 13px;
    background: url('checkbox_sprites.png') -10px -10px;
}

.demo2 .checkbox__input:checked::before {
    content: '';
    background: url('checkbox_sprites.png') -43px -10px;
}

 
<label class="demo2">
    <input type="checkbox" class="checkbox__input">
    Фильтр
</label>