What do you mean, "within the image"?
Discussing the matter withing the image description. The problem would be the missing documentation when the picture is deleted.
I would prefer to discuss on the talk page, it should be separated so that if the result is 'keep' the debate is still around without diving into the history.
What about simple daily pages like we use at http://de.wikipedia.org/wiki/WP:LKB?
There's nothing inherently wrong with that approach... except there are currently 48 days listed on [[COM:DEL]].... instead of the 7-10 you might expect. I don't know that making those ancient debates (back to June 25, what is that, 7 weeks?) less visible is going to make them more likely to be resolved.
Brianna