If you allow users to change their profile pictures or if there are images which are frequently updated by users and those images use a standard name you can work-around browser caching by adding a version number to the image name when it is saved to the disk and stored in a database.

      //Set the image path.
      if (fileUpload.HasFile)
      {
        try
        {
          string imageFilePath = PortalSettings.HomeDirectoryMapPath;
          string imageName = USER_IMAGE + "." + 0 + ".jpg";
          if (!string.IsNullOrEmpty(location.UserImagePath))
          {
            //Find out what version the current file is at
            string[] parts = location.UserImagePath.Split('.');
            if (parts.Length == 3)
            {
              int version = int.Parse(parts[1]);
              int nextVersion = version + 1;
              imageName = USER_IMAGE + "." + nextVersion + ".jpg";

              string oldImagePath = imageFilePath + location.UserImagePath.Remove(0, 1);
              if (System.IO.File.Exists(oldImagePath))
                System.IO.File.Delete(oldImagePath);
            }
          }

          fileUpload.SaveAs(imageFilePath + imageName);
          location.UserImagePath = "/" + imageName;
          imgUserImage.ImageUrl = "/" + imageName;
          imgUserImage.Visible = true;
          AddImageToCache(imageFilePath + imageName);
        }
        catch (Exception ex)
        {
          if (ExceptionHandler.ProcessException(ex, ExceptionPolicy.General, ModuleConfiguration))
            throw;
        }
      }