There was a reason why the "13 Days of Halloween" uploads haven't been uploaded on schedule. You see, I'm sick atm and I really don't have the energy to draw anything. Which sucks, 'cause I have a few days of work to catch up on now.
However, I can tell you the characters I plan to draw next. In no particular order: the Snowdin guard dogs (Doggo, Dogamy and Dogaressa, Lesser Dog and Greater Dog,) Dr. Alphys, Undyne, Mettaton, Catty and Bratty, Papyrus and Sans, Asgore, Flowey and finally Frisk and Chara.
That should cover the rest of the 13 days, including the ones I missed due to sickness. I'm feeling a bit better now, so I think I can get some more work done...