If a radio station is not doing well in the ratings and have consistently ranked toward the bottom, changing imaging will not necessarily improve ratings. A radio station in New York City whose imaging was "Fresh 102.7" and format was sort of a hot AC has been doing poorly in the ratings for many years. They recently changed their imaging to "New 102.7" and did a very minor tweak in their format. Their intent is to compete with with Lite FM 106.7 which has consistently been number 1 in the New York Market for many many years. I have news for them, "it ain't gonna happen!!"
Their "new" moniker will do little if anything to improve their low ratings. Sometimes I don't know what their consultants and programmers are thinking! This station needs to re-think what their doing and probably re-structure the entire format.
It may be a better bet, to change the format completely, re-brand and start over. As I mentioned before, it's better to see slow, steady growth than spikes here and there.