I trust you have set up your CUSTOM template? If not, do so before you edit and save core files.
You need to edit:
includes/templates/template_default/templates/tpl_product_info_display.php
FTP the file to your local machine and then use a plain text editor to edit the file.
You will see the page elements neatly encased in the following comment tag nomenclature:
Code:
<!---bof xxxxxxxxxx -->
(Then some code)
<!---eof xxxxxxxxxx -->
You can re-position these in the order of your choice, so simply find the section relating to additional images, and cut - then paste - it above the element relating to attributes.
Save the file (on your local machine)
Then, FTP the file to:
includes/templates/YOUR_CUSTOM_TEMPLATE/templates/
(... do not overwrite the original file in the template_default location.)