Ask HN: How to tell Google Adsense tags for images?

I am developing a small site that is mostly an image gallery. I would like to show Google Adsense ads that are related to the images. I know various "tags" associated with each image, but these do not appear in the text of the page.

Is there a way to put those tags in the META description/keywords, or will Google Adsense ignore those?

I am not trying to fool the Google page ranking to appear higher in searches, ... I just want to show relevant ads to my visitors.

Any recommendations?

David Jones