Hello again! I believe my response to your original question is here. But just in case: The posting deadline for art is the same as for fic -- November 13th. (I've edited the rules post to make this more clear.)

As for the second half of your question: artists choose which story or stories they would like to create artwork for. This should help you avoid subject matter you would rather not work with. I hope this is what you are hoping for! We would love to see you sign up. :)