If you follow the procedure that Sam has illustrated, you will only get a thumbnail version. The photo is uploaded to the M-Shop server and it lives there.

If you host the photo yourself, using your own space, you can link the photo to your post and everyone can see the full sized photo from your own web space. Presumably, you have a larger photo than the 64K limit here and you can use your own space for it.

You can link any photo that is currently on the the web to your posts at M-Shop. It's a rather cool thing to do once you figure out how to do it.