Using a CSS only approach, add the following CSS inside the content editor webpart or add it to your custom css.
<style type="text/css">
div.ms-promlink-body {
height: 130px;
}
div.ms-tileview-tile-root {
height: 150px !important;
width: 150px !important;
}
div.ms-tileview-tile-content, div.ms-tileview-tile-detailsBox, div.ms-tileview-tile-content > a > div > span {
height: 140px !important;
width: 140px !important;
}
div.ms-tileview-tile-content > a > div > img {
max-width: 100%;
width: 100% !important;
}
ul.ms-tileview-tile-detailsListMedium {
height: 100px;
padding: 0;
}
li.ms-tileview-tile-descriptionMedium {
font-size: 11px;
line-height: 16px;
}
div.ms-tileview-tile-titleTextMediumExpanded, div.ms-tileview-tile-titleTextLargeCollapsed, div.ms-tileview-tile-titleTextLargeExpanded {
padding: 3px;
}
div.ms-tileview-tile-titleTextMediumCollapsed {
font-size: 12px; !important;
padding-left: 6px; !important;
}
li.ms-tileview-tile-descriptionMedium {
font-size: 11px;
line-height: 14px;
padding: 3px;
}
</style>