When I add an image to a post which I already have uploaded to my server Live Writer shows the wrong dimensions in the taskpane. If the image is 430 x 220 pixel Writer shows 43 x 22 etc.
I'm using the "Insert picture" button but I don't use the "From Web" tab in there, instead of that I'm putting the link to the picture into the file name field of the local browser and press "insert". I do this to save one click which would I need to switch to the "From Web" tab and it works as for getting the picture into the post, just the dimensions are shown wrong - not a big deal, I just wondered about the reason :)
If you want to save even more clicks, instead of copying the url, copy the actual image(via right click) and paste it directly into the editor. We will auto-hotlink the image to the remote image. -Brandon Turner [MSFT]