It seems that the NYCC is trying to catch up to the SDCC, with exclusive stuff... as this year the NYCC has some comic cover exclusives on offer.
For Transformers, they have an variant on the IDW #12, which should actually see a wrapping up of the current story arc.
The cover is a homage to Xmen #1... which I'm not sure why - surely a homage to a *Transformers* comic would, you know, make more sense...
As to why certain characters are on the cover:
The TF cover features Sideswipe, Prowl, Swoop, First Aid, Brainstorm, Bombshell and Scrapper... The reason we have chosen these specific characters to grace the covers is because they were all voiced by legendary voice actor Michael Bell who will be joining us at the convention, signing comics, figures, DVDs etc...