Your comments

Ah, gotchas. I apologize, I hadn't realized that there are two possible feed layouts. I have my feed set to use the list format instead of the thumbnails, so this was my first time seeing that.

In that case, I think I would rather suggest something closer to what SoFurry does for tiled views. Again, more informative than an image, and definitely better than the blank thumbnail above:

This is true on sites like FurAffinity and Weasyl, where the only thing seen about a written work is the preview icon and possibly a very small title. In my experience on both of those sites, leaving the icon blank or using an image of the title and keywords was visually unappealing, and resulted in very little traffic.

On the other hand, FurryNetwork already has a far superior interface when it comes to browsing for stories. While browsing, stories have four quickly visible pieces of information: a title, a brief summary line, space for a teaser/preview, and keywords. This gives somebody browsing plenty of information to decide if they want to see more of that submission. My main concern with adding story icons or cover images would be if they somehow overshadowed the four pieces of information above, which I think are far more important and more indicative of a story's content and quality. If they could be implemented in such a way that they didn't overshadow said information or become mandatory in order to get traffic, I would be entirely fine with them.

I tend to be against this, but it would depend on how it was implemented into the design. When story icons or cover art dominate the preview, it almost makes purchasing art for a story mandatory in order to get any traffic. If the title and teaser maintained their places of prominence, I could see this working well.

In order for this to work effectively, the character limit for stories will need to be upped first. >65000 character stories aren't uncommon on SoFurry.