/// <summary>
/// Downloads the image and adds it to the sign.
/// </summary>
/// <param name="request">The requested <see cref="DownloadRequest"/> instance. </param>
private IEnumerator DownloadImage(DownloadRequest request)
{
    if (ItemManager.itemDictionaryByName.ContainsKey(request.Url))
    {
        request.Url = string.Format(ItemIconUrl, request.Url);
    }

    //================================================
    //================================================
    //================================================

    UnityWebRequest fileSizeRequest = UnityWebRequest.Head(request.Url);
    yield return fileSizeRequest.SendWebRequest();

    // Verify that the HEAD webrequest was succesful.
    if (fileSizeRequest.isNetworkError || fileSizeRequest.isHttpError)
    {
        signArtist.SendMessage(request.Sender, "WebErrorOccurred", fileSizeRequest.error);
        fileSizeRequest.Dispose();
        StartNextDownload(true);
        yield break;
    }

    string fileType =  fileSizeRequest.GetResponseHeader("Content-Type");
    ulong fileSize = ulong.Parse(fileSizeRequest.GetResponseHeader("Content-Length"));

    bool wrongFileType = fileType.IndexOf("image", StringComparison.OrdinalIgnoreCase) < 0;
    bool fileIsTooLarge = fileSize > signArtist.Settings.MaxFileSizeInBytes;

    if (wrongFileType || fileIsTooLarge)
    {
        if(wrongFileType)
            signArtist.SendMessage(request.Sender, "File is not an image", signArtist.Settings.MaxSize);

        if(fileIsTooLarge)
            signArtist.SendMessage(request.Sender, "FileTooLarge", signArtist.Settings.MaxSize);

        StartNextDownload(true);
        yield break;
    }

    //================================================
    //================================================
    //================================================


    UnityWebRequest www = UnityWebRequest.Get(request.Url);

    yield return www.SendWebRequest();

    // Code
}