binary image for facebook sharer

See more:

ASP.NET

Facebook-API

, +

hello all
I'm stuck in something and bothering me so much
I want to share some contents of my website too facebook
base url form share is:
https://www.facebook.com/sharer/sharer.php?s=100
I'm sending some parameters like [summary] [title] and ...
when I want pass the thumnbail(the size is: 100*100 px)
it will not shown in share dialog I think it's because I store my images in database and the are binary and I've create Generic handler(.ashx) file to receive images from database.
I pass image like this:
http://mydomain.com/ImageReader.ashx?ID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
it wil not shown in share dialog for faceboon.
what can I do?
please help me
I can't have real images and I have to store them in database
thanks a lot