There's nothing wrong with the game :3 It's just your friends don't see it because they haven't downloaded it. The only "solution" is for them to download the texture pack.
I have downloaded the same modification before, but I eventually ended up reinstalling. This was a while ago, however I think its only changes were to the material files by adding an ambient. I'd recommend downloading this (http://adf.ly/2262836/http://www.mediafire.com/download/2h3551xrc43cb5o/media.zip) and taking the folder called "materials" and replacing it with the one located in Feralheart\media. If that does not work, I'd recommend reinstalling the entire game, however make sure you save any presets, maps, etc somewhere else before uninstalling.
(Edit: Here's some other default files if needed, such as masks, etc. http://www.feral-heart.com/index.php?option=com_jfusion&Itemid=2&jfile=index.php&topic=44252.0 (http://www.feral-heart.com/index.php?option=com_jfusion&Itemid=2&jfile=index.php&topic=44252.0) )