Exporting data from WoW?

[Freeda]

I'm in charge of a guild bank and I have set up a page on a website that displays the current inventory of our guild bank char. However this is rather time consuming so I am going to try and make an addon that would read the contents of the backpacks and the bank vault. I know this can be done, thottbot and others export data that is sent to their server.
I have spent some hours reading about addons and Wow-commands and I still don't know how to do it. It doesnt matter that I have to transfer the data myself, just as long as I can get it out of the game.

Also, I would like to display the data like they do on sites like thottbot, with an icon and a rollover function like the one in-game (tooltip). Making the tooltip appear is trivial, just a little scripting, but I was wondering how the images are collected, are they collected while playing or do I have to pull them out of the MPQs and convert the BLP files manually and have them all hosted on my website. I vaguely remember seeing that some of the data you can access is the item texture, but that is probably just the name of the texture file and not the texture itself?

Hope someone can assist me or at least point me in the right direction.