These are in
/lang/lang_stats.php. Check out the lang folder, I'd say around 90% of the visible text is there. If it's not, it's probably in the view folder.
The icons found on tabs are known as favicons. In your template's header (
/templates/***/header.tpl) you can define this. For example, the code in the default main theme is this line
{$header->loadFavicon("{$home}favicon.ico")} and it looks in the root folder of your site for the file
favicon.ico. Your favicon does
not have to be a .ico file, but if you change it, you'll want to change it where it's loading it, too.
More:
helpful favicon making tool (make it there, or on the left, import an image)
code documentation/guide for Mysidia code I'm working on (very much a work in progress)*
*
I'm not staff or official tech support nor did I make any of the base coding for the Mysidia framework