Changing affiliate image

Hi,

i am working for a company that runs a webpage where fashion blogers can register theyr blogs and users can comment on these blogs and rate them.
For this each user can create one or more nodes each representing a blog (including url, twitter, rss-feed URL ...).
We think that users might be interested in linking this node on theyr blog itself so that they get more votes on our site.
Currently when a User shows his/her own blog-node he/she sees a block with a textarea that contains html code that code mainly consists of a link to the current page and a image within that link. The user is asked to copy this code to his/her page.

What we want now are two things.
First we would be interested in a uniqe image URL for each blog so we can analyse which blog generated clicks to our site.
Second it would be cool to be able to change the image on a per blog basis. The idea is that a blog can have a "gold status" and the image on the page of the blog would change automaticaly when we change the status of the blog to "gold".

Can someone tell me how to do this?

Thanks
angel