Hello,
i was able to translate most of the english terms in italian except this two:

"Click to enlarge the image" which shows on the image thumb mouseover;
"Download this image"

Can you please suggest me how to do it?

Thank you

Hi,

The language file of Simple Image Gallery is located under /administrator/language/xx-XX/xx-XX.plg_content_jw_sig.ini .

Just copy the English file into the Italian folder and change it's prefix. Then edit the contents of the copied file to meet your needs.