Windows 8 – Add Headings to Start Screen Tile Groups

1. Open the Clock, Language, and Region section from the Control Panel:

   

2. Open the Language panel:

   

3. Here we can see the issue:

   

   To resolve your language conflict, add a new language

4. Open the English language catalogue:

   

5. Pick whatever English language you prefer and Add it:

   

6. Open the Options for your newly added language and add a new input method:

   
   

7. Pick the Slovenian keyboard layout, add it and save your setup:

   

8. You can now Move up your new configuration and Remove the old one.

   

   Your date, number and time formats should still be set to Slovenian:

   

9. Restart Windows.

10. Success

    

Tiles for Modern UI apps will use the background color of the application.

From here: http://social.msdn.microsoft.com/Forums/en-US/winappsuidesign/thread/edf26bd7-0fd0-4cef-bd0f-dcc7399c0f3f

Your tiles will use the background color of your application. This is specified in your Manifest in the first Tab.

Tiles for Desktop apps aren't set per tile.

From here: Set color for desktop application's start screen shortcut, this answer.

For desktop apps, the background color used on Start screen tiles and toast notifications is not configurable by the app itself. The color is determined by the Start screen color theme chosen by the user (PC Settings -> Personalize -> Start screen).

If you just want to easily group applications together see this answer, on this question:
Named Group of tiles (Applications) in Windows 8?

For creating custom shortcuts to files/folders as tiles see my question here:
Adding custom shortcuts to Modern UI

Any shortcut you create (including switches) you can simply right click and "Pin to start" which will create a copy of it in the appropriate places.

So for example, to add a folder to the start screen, see the answer here, https://superuser.com/a/491169/85165.
Go to the desktop, create a shortcut to the folder you want, then right-click the shortcut, Pin To Start.