styles.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    ... 
    <style name="PersonCardTheme" parent="Theme.Leanback">
        <item name="imageCardViewImageStyle">@style/PersonCardViewStyle</item>
    </style>

    <style name="PersonCardViewStyle" parent="Widget.Leanback.ImageCardView.ImageStyle">
        <item name="android:layout_width">180dp</item>
        <item name="android:layout_height">250dp</item>
    </style>
    ...
</resources>