I entered the code on my time card (Propina). After copying the code, the decoded text is shown below. You type this into a password field that appears, and hit Enter. You then get a partial image of size 2560x1600, which seems to be part of a wallpaper with the Mariachis.
Note: the barcode entry appears to be broken for all versions on IE, including the current IE8 beta.
I'm guessing the other codes unlock the other parts, so you can eventually create a complete image by working together. This makes sense: I saw someone post a picture of a different time card, and I noticed the bar code was different as well (I didn't decode it then, though).
Here's my partial image. As I mentioned in an earlier post, this is the code from the Bosco time card, 1963.1025.