try this code:
check your image extension png or jpg
-(IBAction)serviceSelected:(id)sender
{
UIButton *tmpYes = (UIButton *)sender;
if (tmpYes.currentBackgroundImage==[UIImage imageNamed:@"checkBox.png"]) {
[tmpYes setBackgroundImage:[UIImage imageNamed:@"checkBox_none.png"] forState:UIControlStateNormal];
}
else
{
[tmpYes setBackgroundImage:[UIImage imageNamed:@"checkBox_none.png"] forState:UIControlStateNormal];
}
}