Yes, but you don´t need to do any changes to the db. You will need to modify two files...
In include/staff/newticket.inc.php
Find...
<select name="source">
<option value="" selected >Select Source</option>
<option value="Phone" <?=($info=='Phone')?'selected':''?>>Phone</option>
<option value="Email" <?=($info=='Email')?'selected':''?>>Email</option>
<option value="Other" <?=($info=='Other')?'selected':''?>>Other</option>
Replace with....
<select name="source">
<option value="" selected >Select Source</option>
<option value="Phone" <?=($info=='Phone')?'selected':''?>>Phone</option>
<option value="Email" <?=($info=='Email')?'selected':''?>>Email</option>
<option value="Other" <?=($info=='Other')?'selected':''?>>Other</option>
<option value="your_option1" <?=($info=='your_option1')?'selected':''?>>your_option1</option>
<option value="your_option2" <?=($info=='your_option2')?'selected':''?>>your_option2</option>
<option value="your_option3" <?=($info=='your_option3')?'selected':''?>>your_option3</option>
In include/class.ticket.php
find...
if($var && !in_array(strtolower($var),array('email','phone','other')))
Replace with..
if($var && !in_array(strtolower($var),array('email','phone','other','your_option1','your_option2','your_option3')))