Hmm... I cast my vote for your OC's, and I noticed some people selected the OC/human answer... But what about your OC's as ponies? I feel that this field of OC manipulation has not yet been fully appreciated and should be consid- -killed by Naigo- XD
You know I was waiting for this pole to be submitted. What I would recommend is two options really. One would be that you develop your existing characters and who they are, their relationship with one another, and what is their purpose and goals in life and make something with that. The other option I suggest is find a common setting\ theme all or most of your characters fit into and go with that.
I would also like to it be absurd but have hint of realism in it just to make seem more grabbing. However it is admittedly hard to do a story with the giant theme. Doesn't mean you should get away from it. I'm fine with a story as long as there's something new to it. But that is solely my opinion and in my opinion alone nothing more.