Those watching the floor vote might have noticed that the states were called out in alphabetical order, but that states were not seated that way. Alabama was in a totally separate spot on the floor from American Samoa and Arizona, for example. That's because seating order was determined separately from voting order. The delegations with the best seats include a lot of swing states- Virginia, Wisconsin, New Hampshire, Ohio, and Pennsylvania all have prime seating assignments very close to the podium. Romney's home state of Michigan is seated front and center- a clear indicator of the campaign's desires to make Michigan a swing state. Massachusetts, the state that launched Romney's political career, also has a front row seat. These seating arrangements change with every cycle as well- but frequently states of particular political or personal importance to the candidate generally receive good placement.
The other two purposes of the convention are to adopt the party's platform and principles, and rules for the next election cycle, including the procedure for selecting the presidential candidate for years later.
Conventions serve a very important cultural function too. They're the springboard, so to speak, for the final months of the electoral push. The party comes together to rally behind its chosen candidates, and voters who may not have been paying attention to the election suddenly take notice of the candidates. The convention provides a symbolic moment of pride and enthusiasm, and an opportunity to show party strength.