yes, that would be correct. If both the previewimage and image fields are NULL, then the module will use the "no image" image.

on the Repository's module settings page, at the bottom, what do you have selected for the "no image" file? make sure you have selected an image that exists. maybe try selecting another image and see if that helps.

Ok.  I am feeling foolish.

I installed a brand new install of DNN to see if I could replicate the problem I was having. After installing DNN I installed the Repository Module. I went to settings to see if the "no image" setting was there. Of course it was. Not like I was expecting, in the form of a text box like the folder settings, but in the normal url/file location/name format. Big oops for me.

As a suggestion, to make it easier for people who have a hard time reading past where they expect something to be... like myself... that setting configuration could be tightened up a bit. (Remove the space between the title "No Image" and "Link Type".)