Get attachment thumbnail for use in CSS hyperlink background

So this seems pretty complex for me:

For my category archives, I want thumbnail links to single posts, except I want the hyperlinks built CSS backgrounds made from the thumbnail of the one image attachment in each post (with text-indent offset), not img tags.

Basically I need to have the links use only text values because jquery is parsing the hyperlink text for a function. Having img tags between the hyperlink tags ruins the function, so I can’t have them there.