The way that you upload a picture is to post it in a picture hosting site like tinypic is what I use.
TinyPic - Free Image Hosting, Photo Sharing & Video Hosting
once you upload the picture it will give you the code to post on a forum or message board as one of the options. After you have copied the link of the pic take it back to this page and where you type a reply for this in the message box click the little box above, its the second to last one that looks like a landscape with mountains. paste the code into there but erase the IMG at the end along with the punctuation marks.
What you might want to do with a tank that big is find some plants that can grow pretty tall to fill the empty space, also adding bubbles could be a fun thing to watch rise to the top. Plants like this might be your best bet because how hard its going to be to clean this tank. choose the correct substrate and the fish waste will be used as nutrients for the plants.
Just my thoughts, hope I helped.