I have a content type which has an attached image, I have a view which displays the nodes in rows with the image thumbnail at the far right on each row.

If image:attach does not exist for the node, I want to display user:picture, or a default image in its place.

I can add both image:attach and user:picture to the fields displayed, where they both appear in the view, but I only want user:picture field to appear if image:attach doesn't exist.

I know this can be done quite easily and quickly with theming, but I'm not an expert in this area.