In holo theme, the tab only support label or icon and mutually exclusive.
After Holo, as a default the tab supposed only have label, please check the design guideline. http://developer.android.com/design/building-blocks/tabs.html
If you willing to both label & icon at the same time, there are two options.
Option 1: Using old Gingerbread theme. Set your android:targetSdkVersion 9 or below. (Before Honeycomb)
Option 2: Using custom layout & view for your tab. Of course, it required some efforts, but you can use any custom layout what you want. For example:
in your activity code:
TabHost.TabSpec ts1;
View tabView = getLayoutInflater().inflate(R.layout.custom_tab, tab_host, false);
ts1 = tab_host.newTabSpec("TAB_ONE").setIndicator(tabView).setContent(R.id.edit_species_tab);
in your layout: (whatever you want)
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/tab"
android:layout_width="80dp"
android:layout_height="wrap_content"
android:orientation="vertical">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello"
/>
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_launcher"
/>
</LinearLayout>