more upgrades for each room(type)! better washing machines, faster internet access, more games in the arcade, room service, bigger TV in the rooms, ...
playground (high mountain) is hiding the countdown,
weapon description with damage per shot needed,
option for friendly fire would be good (maybe even double damage to teammates),
how about maps where you can leave on the left side and enter on the right?
flying packages adding double damage or larger explosion radius were cool!