PNG images, but I can't open them

[Davy Jones]

Here is an example:
https://www.file-upload.net/download-127...0.png.html
Size: 17,6 kilobyte.
File extension: PNG

This is from Orc Castle, a PC game. Apparently, the game uses a special PNG version (?) to hide its graphics. Manual Pictures, cursors, etc. are displayed, but the rest can't be opened.

Is there any trick to it?

[puggsoy]

OK that's fricken weird. I was expecting there to just be some junk at the front of the file but it looks either compressed/encrypted or just a completely different format. Would you mind uploading a few more?

[Davy Jones]

Here you go, every file from 1 to 99 kilobytes:
https://mega.nz/#!VdIGQSRb!lgLVzNH1whWIJ...E26Ov_N4Oo
Size: 2,8MB
File extension: PNG

[puggsoy]

What I've gathered so far:

0x00: "EENC" header
0x04: File size after this point (little endian), i.e. file size - 8

So it has some structure at least. The extremely small sizes suggests compression though, which is bad news since I can't find anything on it online :\

[Davy Jones]

Just what I thought, these are encrypted and used for hiding the original pictures. Here are some bigger ones:

Everything from 100-999 kilobytes:
https://mega.nz/#!gY5EQB4L!mCFa8dlfnwqnm...kHJMkc8X9o
Size: 114,9MB
File extension: PNG

By the way and just if it helps:

Here is a encrypted file with the name 00020100.png, this one is from me:
https://www.file-upload.net/download-127...0.png.html

And now this is the same file, but from the internet, decrypted and therefore viewable. It was also named 00020100.png and is an actual file from the game:
https://i.imgur.com/0yGGWiz.png

Someone on the internet was able to decrypt the compression, I already messaged him but I'm not sure if he responds. Could you take a closer look how he possibly did it?