Nevermind... after some more tweaking, I figured it out.
For anyone who may need help on how to do this, I've included the code I'm using below. Simply adding another line "imagestring" with updated variables on the location of the image you want the text will do the trick.
header("Content-type: image/png");
$im = imagecreatefrompng("images/1.png");
$font_a = 4;
$xpos_a = 5;
$ypos_a = 25;
$string_a = "$username";
$font_b = 2;
$xpos_b = 5;
$ypos_b = 42;
$string_b = "$email";
$font_c = 2;
$xpos_c = 5;
$ypos_c = 58;
$string_c = "$data1";
$font_d = 2;
$xpos_d = 5;
$ypos_d = 74;
$string_d = "$data2";
$white = imagecolorallocate($im, 255, 255, 255);
imagestring($im, $font_a, $xpos_a, $ypos_a, $string_a, $white);
imagestring($im, $font_b, $xpos_b, $ypos_b, $string_b, $white);
imagestring($im, $font_c, $xpos_c, $ypos_c, $string_c, $white);
imagestring($im, $font_d, $xpos_d, $ypos_d, $string_d, $white);
imagepng($im);