Yeah, it could definitely be some new type of ship. It is just really hard to tell based off of the angles they provided. Maybe it is someone from the future trying to get revenge on the changes in the past movie, someone like Picard or something. That would be interesting, but kind of a weird story.
It would be weird but I hope to god that is not a Galaxy Class ship, the Galaxy Class was a good looking ship and to be honest that thing is just any ugly brute. Only thing we have to remember is that The Enterprise only became the flag ship of the fleet and ergo the most advance ship of the fleet from The Next Gen onwards, before that it was just another ship of the Fleet and in some cases (Search For Spock) it was nowhere near the biggest and most advanced ship of the fleet.
As trek fan my position on the new Trek reboot? Well the problem is the word reboot. I have no really issue with the every minute has action, wobbly camera, explosions everywhere, lense flair, little character, action drives story rather than story drives action movie making style that the new movies are going for and had this been set in a post Voyager Trek Universe it would be fine, it's Star Trek and it's going in a new direction, fine, but taking the established canon and throwing in a new look and style, basically trying to rewrite the history but pushing it aside under the guise of alternate time line, well that doesn't wash I am afraid.
I recon the backlash from Trek fans would be much smaller if it had been set post Voyager rather than trying to rewrite the History, I make that assumption on what happened with Stargate Universe, that went in a different direction to SG1 and Atlantis, loved SG1 and Atlantis and fucking hated Universe but apart from them trying to rewrite the way the Stargate worked in the first episode I couldn't care less after that because they didn't really try to change what had come before.
I am gonna see this movie I hope that this alternate timeline story has some carry through and wasn't just used in the first movie as a way to split off from the established canon and do whatever the hell they want with it because you know 'alternate timeline'.