If you don't already have the germ of an idea it might help to just sit and brainstorm a whole bunch of things that nominally fall into one or more of those categories. It could even be something you've taken from a videogame or another game's monster manual that you want to convert or reconceptualise. It could be a myth (Spring-heeled Jack), a phrase (Kissing the gunner's daughter), a particular fear (disease), body part (eyes), visual (sparkling waterfall) or even the scrap of a fantasy or dream (an elk whose eyes are full of wisdom yet is hunted through the forests). This might be a setting either simple (haunted house) or complex (tunnel connected to cellar in a tannery leads to ethereal domain where the souls of butchered animals clot into strange entities). There's plenty of strange allowed in urban fantasy and personal horror, after all. You'll find plenty of worth in the following notes for creating unknown creatures for your own campaigns set in the canonical world. If you're not planning on using the mod and just want vanilla World of Darkness, never fear. I'm capping it at 20 weeks worth of topics.
This is because I've found that there's a lot needed even for a WoD mod to truly open it up and make it useful so I've added in more labels as I think of them. If you've already read that main post and re-read it you'll find that I've added a whole bunch more article entries though they may not all have links attached yet as they'll be released weekly in each category. The rest of the articles on this World of Darkness modification for a fantasy world can be found here.