方式一： 使用AFNetworking，可以在UIImageView+AFNetworking.m第64行添加一下代码：

- (void)setImageWithURL:(NSURL *)url placeholderImage:(UIImage *)placeholderImage token:(NSString *)token {
    
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    [request addValue:@"image/*" forHTTPHeaderField:@"Accept"];
    [request addValue:token forHTTPHeaderField:@"token"];
    
    [self setImageWithURLRequest:request placeholderImage:placeholderImage success:nil failure:nil];
}

方式二：（推荐） 使用SDWebImage来加载

// 导入头文件
#import <SDWebImage/UIImageView+WebCache.h>
#import <SDWebImage/SDWebImageManager.h>

SDWebImageDownloader *loader = [SDWebImageManager sharedManager].imageDownloader;
[loader setValue:Token forHTTPHeaderField:@"token"];
[self.imageView sd_setImageWithURL:[NSURL URLWithString:imageURL]];