I found the solution:
Just remove a Regedit entry, and you´re done...
Find your user's ID on HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\hivelist.
It should be the entry that includes the user's name on the value information. Example: \Device\HarddiskVolume2\Users\{USERNAME HERE}\NTUSER.DAT.
Take note of the long string at the end of the name of the entry. Example: \REGISTRY\USER\{LONG STRING}.
Now go to go to HKEY_USERS\{LONG STRING}\software\classes\.png\shellex and delete E357FCCD-A995-4576-B01F-234630154E96.
Then restart, and all icons will be normal again.