Navigation back buttons themed like iOS7, for iOS 5 and 6

gistfile1.m

-(void)themeBackButtons
{
  // Appearance proxy methods
  [[UIBarButtonItem appearance] setBackButtonBackgroundImage:[UIImage backButtonImage] forState:UIControlStateNormal barMetrics:UIBarMetricsDefault];
  [[UIBarButtonItem appearance] setBackButtonTitlePositionAdjustment:UIOffsetMake(7.0, 0.0) forBarMetrics:UIBarMetricsDefault];
}

// The image above is generated by this method
+(UIImage *)backButtonImage
{
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(30.0,22.0), NO, 0.0);
    UIBezierPath *arrowPath = [UIBezierPath bezierPath];
    CGFloat edge = 13.0;
    CGFloat lineWidth = 3.0;
    [arrowPath moveToPoint:CGPointMake(0.0, edge)];
    [arrowPath addLineToPoint:CGPointMake(0.0, 0.0)];
    [arrowPath addLineToPoint:CGPointMake(edge, 0.0)];
    arrowPath.lineWidth = lineWidth;
    [arrowPath applyTransform:CGAffineTransformMakeRotation(-M_PI_4)];
    CGRect pathFrame = [arrowPath bounds];
    [arrowPath applyTransform:CGAffineTransformMakeTranslation(lineWidth, pathFrame.size.height * 0.5 + lineWidth * 0.5)];
    // Put your app's theme colour here
    [[UIColor redColor] set];
    [arrowPath stroke];
    UIImage *returnImage = [UIGraphicsGetImageFromCurrentImageContext() resizableImageWithCapInsets:UIEdgeInsetsMake(0.0, edge, 0.0, 1.0)];
    UIGraphicsEndImageContext();
    return returnImage;
}