hmmm......if it isn't a joke then it is bound to be something to look forward to.
Users very active on IRC might have more info..

Conspiracy Theories
This is most likely a joke, but after contrast:

Any ideas?
Edit: EXIF data analysis from exifdata.com
File Size 115 kB
File Type PNG
MIME Type image/png
Image Width 741
Image Height 495
Software paint.net 4.0.3
Compression Deflate/Inflate
It also looks a bit like a Rorschach test
EDIT: Well, it definitely is the first image of the official Rorschach test, shown on Wikipedia:

Now why should there be a Rorschach test in Powder Toy...
SUPEREDIT: I've just realised the Rorschach test was uber-simple to see in the original, I've just loaded it up on my awesome monitors and I can see it. My laptop wasn't powerful enough xD

EDIT 2: The tptapi site has been updated with this
EDIT 3: It looks sounds like it's SSTV (Just like in the Portal radio ARG) but I can't decode it as I don't have a dedicated sound card.

@CeeJayBee (View Post)
I don't think it's gonna be a joke. Unless Simon decided to do the joke he missed this April 1st for Christmas...
And yeah, it is the first image of the Rorschach test.

@greymatter (View Post)
Decoding the SSTV would be useful. If you have a graphics card that'd be easy. You can download the SSTV software I tried to use here. All you do is play the sound through the sound card and press "RX" to start decoding (as far as I know). The filename is TX 12352 which seems like a US zip code from Texas, but I haven't been able to find an address yet.

@boxmein (View Post)
boxmein pls decode sstv

pls

EDIT: Another edit!
Next to the sound file it now displays: Address the carriage when the url is on file, after the message is understood s/C