Often, wards and branches take on the personality of the Bishop or Branch President. Auxiliaries often do the same thing in modeling their individual presidents. This can be alleviated by a visible counselor who has a different personality, but leadership style and personality are strong indicators of the type of vibe within a ward. That cuts both ways, unfortunately.
Having said this, I have witnessed one ward where an out-going, loving, smiling sister with no major calling almost single-handedly changed the spirit in a ward. It was impossible to be anything but happy around her - and she was "around" everyone all the time. It is hard to describe how her spirit of joy and love affected the other members of that ward; it's hard to understand how pervasively her influence was felt. Thanks, Sis. A.
My advice: Be the change you want to see and pray that others will follow your lead. (Just don't get judgmental about it.) Oh, and smile as you put yourself around people as much as possible.