4-Piece puzzle [Giveaway ended]

This is my first puzzle-giveaway and it's probably rather easy.
All you have to do is find all four puzzle pieces and add the letters and/or numbers on them to a steamgifts URL like this:
http://www.steamgifts.com/giveaway/***** (using the letters you found instead of the asterisks of course).

So here is your first piece: First piece

The other three are hidden somewhere (at least one of them should be obvious, though).

EDIT2: The giveaway is over now, the game given away was the Syberia bundle: http://www.steamgifts.com/giveaway/M5K8U/syberia-bundle

The first piece was simply given to you in this post.

The second piece was my avatar while the giveaway was open.

The URL to the third piece was hidden in the list of previous profile names in my Steam profile.

The URL to the infamous fourth double-piece was hidden in the properties of the first picture. The way to find this I thought of when creating the puzzle was to save it and check the properties offline (right-click -> properties in Windows) or use one of several online tools to read picture's meta data if you don't like to save anything on your computer.
Looking at the properties with the Opera browser showed it as well, Firefox and Chrome apparently not.