You're using the wrong MIME-type header for an HTML document. You aren't sending an image to the user, you're sending an HTML document. Try:
use CGI qw(:standard);
use CGI::Carp qw(warningsToBrowser fatalsToBrowser);
print header('text/html'); # Sends Content-type: text/html;
"Hello i'm working",
"<center><img src= \"http://127.0.0.1/cgi-bin/images/test.jpg\" ></img></center>",
Your code relies on a lot of functions built into the CGI.pm module for creating the essential components of an HTML document. While it does make it easy and you can control all of the elements, the code can get a bit complex when you want to create a working page with a lot of tags in the <head> section. So, you might consider creating those elements yourself in your scripts in the future.
Sixtease was also correct that the http://127.0.0.1/ will only work on your local computer (assuming you have installed Apache and Perl on your own system). So remember to change the <img> tag if you put this script online.