Thanks to Da Razorclaw at TFWorld2005.com for pointing out that a game on the Cartoon Network Transformers Animated website includes some pictures of previously unannounced and some announced, but not previously seen, characters.
This is a pretty nice on-line battlecard-type game. I've found its pretty addictive.
The real news is that it reveals some new characters! In addition to
giving us our first clear looks at Prometheus Black, Headmaster, and
Nanosec, it also reveals that Ironhide and Scrapper are future
characrers!
It seems there are also two more playable decks yet to be added; the computer can use them, though, it seems.
Scrapper and Ironhide can only be seen in the opponent's decks, thus far.