I’m not a terribly experienced WordPress user, but I did some tinkering and found out the problem lies with the theme I’m using, “Parabola.” I’m guessing there’s a conflicting file buried somewhere in that package. I checked the obvious photo settings, but nothing changed Post Tiles from displaying links to images as blank/black “posts.”
Again, I’m not terribly experienced, so I’m not sure where to go from there, so I guess I’m just going to have to disable Post Tiles for now and check it again when Parabola updates, sometime.
Thanks again for all your help.