By the looks of previous posts people seem to like bears in forests. Are they innocent, friendly bears? Or angry grizzlies? (Or lycanthropes, as Agar suggests)
You enter the clearing to find a huge and terrifying bear looming angrily over you. You instinctively draw your sword, trying to remember if you're supposed to act dead or act threatening. After a few breathless seconds of agitation, you realise that the bear is dead. It facial expression is not one of anger, rather one of contorted agony. It has been preserved and nailed to a tree.
I have been getting into H P Lovecraft lately. Dreams are such an important part of his work that it would seem a pity to leave them out of a Cthulhu game. One idea I tried was compiling a collection of paragraph-long dreams (much like this scroll) and occasionally handing them out during play when the PCs were sleeping. I was going to post them separately, but then I noticed this thread already exists, so here is a short compilation:
More abstractly, it might be an interesting experiment to have a parallel plane of existence accessible by dreamers but particularly by feverish and impressionable artistic types (I'm thinking of course of Lovecraft's dreamlands). What would make this interesting would be concealing the fact from the players. Occasionally you could force PCs to play out the dreams they're experiencing (while my former suggestion was for them just to be read). This would be particularly effective with dreams where they are being chased. Have them suspect that the rolls they are making could mean life-or-death. Maybe the first few times, when they die in the dream-world they just wake up again. As time goes on, maybe the effects become more severe, with real-world HP losses. At the same time they might be able to work out that they can control things to some extent and that there is more to this parallel world than a simple dream. At some point it will dawn on them that there is something to be explored.