checked.xml
<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient android:startColor="#ffff0000" android:endColor="#ff000000" android:angle="270"/>
<stroke android:width="4px" android:color="#ffc0c0c0" />
<size android:height="20dp" android:width="20dp"/>
</shape>
Unchecked.xml
<?xml version="1.0" encoding="UTF-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<gradient android:startColor="#ff585858" android:endColor="#ff000000" android:angle="270"/>
<stroke android:width="4px" android:color="#ffc0c0c0" />
<size android:height="20dp" android:width="20dp"/>
</shape>
custom_checkbox.xml
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:state_checked="true"
android:drawable="@xml/checked" />
<item android:state_pressed="true"
android:drawable="@xml/checked" />
<item android:drawable="@xml/unchecked" />
</selector>
E poi nella vostra xml
<CheckBox
android:id="@+id/checkbox2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:button="@xml/custom_checkbox"/>
Per maggiori dettagli si veda questo blog e Custom checkbox image android.
Spero che questo ti possa aiutare.
possibile duplicato [L'aumento delle dimensioni della casella di controllo] (http://stackoverflow.com/questions/7324036/increasing-the-size -del-check-box) – Kyle