I show that Image::Size is installed on NINE. I'm not sure if it is installed on your server or not, althoug I would expect so. To check, you can go to your CNC control panel, located at
(but replace 'yourdomain.com' with your actual domain) and click on "Server Info" and scroll down to where it says "Perl modules" and click on the link "Click here for module info". This will take you to a listing of ALL the Perl modules installed on your server.
When I installed Moveable Type a few weeks, back, I found that Image::Size was installed, but HTML::Template was not.
However, the documentation for Moveable Type has pretty good directions on how to install any modules that you may need, if they are not already installed. I did have to install the HTML::Template module, but I followed their directions and it worked quite well. If you find that Image::Size is not installed on your server, then you can follow the directions in the Moveable Type documentation for installing that module as well. (see the file mtinstall.html in the doc folder)
Hope his helps.