Sold Sign Overlay on Images

[johnlanglois]

I think I have asked this before, but never received an answer.
Is there a way to have a "SOLD" sign over properties which are no longer for sale?
I am using an extra field to track availability as either "Available" or "Sold."
For those that are sold, I would like to have the CSS process a text banner and layer it over the image.

Where is the code that processes the building of the page view of properties in a particular category?

Has someone already invented this wheel?

Thanks.