Да, вы можете сделать это -
UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeCustom];
UIImage *homeImage = [UIImage imageNamed:@"YOUR_IMAGE.png"];
[backBtn setBackgroundImage:homeImage forState:UIControlStateNormal];
[backBtn addTarget:self action:@selector(YOUR_ACTION)
forControlEvents:UIControlEventTouchUpInside];
backBtn.frame = CGRectMake(0, 0, 69, 26);
UIBarButtonItem *button1 = [[UIBarButtonItem alloc] initWithCustomView:backBtn];
[[self navigationItem] setLeftBarButtonItem:button1];
[button1 release];
button1 = nil;