HI Sky,
You can create a new language pack by editing the existing language pack. Here is the steps:
1. Download any language pack from our site. Example: en-GB_com_easysocial
2. Edit these files and save it as your own language pack. Example: st-ST_com_easysocial
3. Install it through Extension Manager. Now you have it.
However, to use this language pack in your site, your Joomla also must have the same language and set it as default. You can create this using the same steps as above. Please give this a try and see if this resolves your issue.
Please do update us back on this issue.