Is it possible to use those available Icons as a shortcut for categories?
Can you please explain your question further? Are you talking about actual WordPress categories, or are you referring to minisites? And when you say "shortcut" what do you actually mean - how would the icons be a shortcode?
I would like to use those icons in order to link them to my site categories. Do you understand?
Which icons? Is there a screenshot or something to help me understand?
This Available icons. http://www.industrialthemes.com/flavor/shortcodes/
Yeah you can use those icons i guess. You have to upload it and then you can select respective icons for each minisite.
You can't use those for your minisites because they are not image files, instead they are actually an icon font. Here are good resources to find your own icons to use though:
I use Flaticon. They also have a photoshop extension which is connected to their website. Really cool.
Awesome resource, never seen that before, thanks for sharing!