I decided on a cartoon style for the graphics, thinking that would be easiest. (By "cartoon style", I mean black outlines with solid fills, limited palette, no shadows or highlights.) I've done three rooms in three days and they're not really finished yet. At this rate, I'll be finished by Christmas. And I've still got a few urgent things to do before the end of the month - like my tax return and prepare a display for another group. Sheesh.
If you can't get the graphics done in time for the 30th, then just try to have them done by the end of the voting phase. It may affect the graphics category in voting and eligibility for prize draw, but I won't apply a strict deadline to having the graphics ready. This is meant to be fun, sorry it sounds like stress for you.
Good luck, and really hope you make the deadline, with or without graphics.
A map (of course) showing the relationship of the rooms, some rough wire frames and lots of images from Google image searches showing the sort of thing I've got in mind. However, I wouldn't expect anyone to jump in now at such short notice. I'll just plug away and do the best I can over the next few days. There are 23 rooms all together. Here's a sample from the ones that are closest to completion:
I haven't done any of the outdoor locations yet.