Recently I am facing the problem with thumbnail image. In the past there was never a problem with thumbnail image size. But now I am getting the message that the thumbnail image size should be less than 50kb. Isn’t it a very small size for graphic river items where you need to make the thumbnail image more attractive by adding some graphics. Please increase the limit to at least 100kb.
Upload it via ftp so there will be no restriction 
You can also do it under 50kb, if you Save for Web.