It seems that if you have a picture that’s over 450 pixels in the horizontal direction, and you choose ‘medium’ for the picture diplay (the default), it will resize the horizontal to 450 and leave the vertical as it was. This creates bad distortion in as much as it produces an ‘elongated’ photo. It is also possible to wipe out the Navigation Sidebar if the photo is too large.
One way around this, is not to choose the ‘medium’ size, but rather, to choose ‘thumbnail’ size instead when in the process of adding the photo.
In this page, you can click on the thumbnail below to get to the original size of the photo that you uploaded. This avoids the distortion problem and the other problem of wiping out the Navigation side bar on the right hand side of your post.
The thumbnail is this case is 92×120 and the actual map is 800×1037.
In my first post ‘Hello World’, the picture was 198×264 and so I totally avoided the problem (accidentally).
So, to sum up, if your photo is less than or equal to 450 x anything, it should work as is. If it is greater in the horizontal direction, then use a thumbnail in your post.
This is the method I would suggest for now. If you can think of something better, please post it.