Hope this helps...
<select name="selectBox1">
<option value="img1.png" style="background-image:url(img1.png);">male</option>
<option value="img2.png" style="background-image:url(img2.png);">female</option>
<option value="img2.png" style="background-image:url(img3.png);">others</option>
</select>
On submitting the form you will get the selected value inside $_POST["selectBox1"]
post variable.
Thanks.