Can't tell you off the top of my head. Posting from your own toybox there is a max that can be got around by toning down the quality of the jpg you want to post. Lower the quality and it will take it.
From a website I can't tell you. Some boards the length of the address will prevent it from being done, it just posts the link.
At my old squad website, I could use a signature card of a long length address. But if I tried the same address in the body of the post it wouldn't do it. It would just post the link.
You can post a link of any size I believe.
Hope this helps..
