I have noticed that many people have started to use Flickr to store their Mars photos. Flickr is a great tool, and I have created a plugin that will make it easily to post thumbnail links of your photos stored in Flickr.
To post a linked thumbnail of a Flickr photo, simply copy and paste the URL of the Flickr photo page into your message. The Flickr photo page is the page on Flickr that displays a single photo. These page have URLs that look like the following:
http:// www.flickr.com/photos/hortonheardawho/93950004/
(Note: when you paste the URL into a message, there should not be a space after the http:// - I have used a space above to prevent the URL from being converted to a thumbnail, so I can illustrate what these URLs look like. )
Here is the above example as a Flickr thumbnail:

Note that these are 'real' thumbnails, not re-sized images. The thumbnails are linked directly to the original size version of the image on Flickr. These linked images will open in a new window.
This feature makes use of the Flickr API. It took me a while to figure it out, but eventually I did.
Please reply with any questions, comments, suggestions, or if you find something broken.