Odd. I thought the URL had to be in quotation marks, but when I tried it both ways on the test page both worked the same.  Neither showed up until I clicked the edit button then both did.

But why go to all the effort?   If you have it on your computer just click the box at the bottomof the page to upload it.

If you really want to link it from an online source, or the photo is not one you have locally, instead of using html just click the button on the toolbar above the dialogue box with the tree on it and upload it from your computer.

Having said that, I have one computer that for some reason nobody has ever figured out will not show the toolbar with those buttons in Firefox.  OK in IE and Opera, not Firefox.  Never did figure that out.

Oh, and using the linking feature you can slide down to the lower right corner of the photo, grab the box on the corner and drag it to the upper left to make the photo smaller. 

Any way, it makes photos simple.  Try it, you'll like it!