Could you just use if/then statements? How many images are you looking at?

Here's what I'd do...
<INPUT TYPE="checkbox" NAME="a" VALUE="1">Image A
<INPUT TYPE="checkbox" NAME="b" VALUE="1">Image B
<INPUT TYPE="checkbox" NAME="c" VALUE="1">Image C

Then instead of doing a Loop (which is kinda cool) I'd just do if/then's

if ($a) {print qq|<IMG SRC="./images/a.gif">|;}
if ($b) {print qq|<IMG SRC="./images/b.gif">|;}
if ($c) {print qq|<IMG SRC="./images/c.gif">|;}