The only thing I can think of that you might be doing is not opening the picture at Image Station in your album and linking to the main picture, it seems your link is to a thumbnail version of the pic. You need to veiw the pic the way you'd like it to post and them rt click on it and select properties... rt click URL there and click "select all", copy that URL and use it. Seems that is what you are doing but, your link is to the thumbnail version is all.
When I post one, I enter (open) an album and scroll through the dropdown list of pics in it or look at each of them to find the one I want to post. When I find the one I want and it displays, the URL on that pic in that window is the one I use, I don't click on the pic to display the pics original size and use that URL... most of the time that pic won't show up is why.
Good luck, any questions, fire away.
Here's a link to an Albumn of mine, if that helps you out any.
http://www.imagestation.com/album/?id=4291028135
After looking at my album here, I think what you did was rt click on the thumbnail pic from the "index" view, at least when I did it, it would have the ".thumb" at the end of the URL there. What you need to do is click on the image to view it as a larger pic, then rt click on that one when it enlarges... it should show up fine then.
You're right, the better the pic is to begin with, the better it will show up here... image station started reducing the size of them when you upload them a couple months ago.
Hope that helps some.