Here is the new trailer released a few days ago. People are claiming that they can see tentacles at the beginning when the store clerk is attacked (00:06) and also behind the electrician (00:11). The tentacles are obvious, but if you watch closely just before the glass breaks behind the store clerk, you can see the monster through the window.
Here is the pic from the trailer above that appears to show the monster's head, eyes, teeth, and some kind of appendage.
"Super 8" hits theaters on June 10th, 2011.