Steviet_scg
For future reference, the address of the file that you need to use is the url of the actual jpg file. In this case that is:
https://lh6.googleusercontent.com/-LWNkpMWAzm4/TgSXFM-1iVI/AAAAAAAABkM/fvki4bGGL-k/who%252520knows.jpg
I got this by right clicking on the image itself on the picasa page, choosing properties and copying the above from the address field in the properties.
If you then put the above in the image tags [img ][/img ] (note that the tags should not have a space before the close bracket - this is just so you can see the code within this message) then you should get what Rob posted.
Using the preview function before posting will also let you verify that the code is correct as it will show a preview of your post at the top of the page.