I took a recent dungeon floor I had setup on a 2’x4′ foamcore board for easy placement and decided to give it the chroma-key treatment. That’s the fancy word for what they do with greenscreens but in thiscase the removed color was white. I used GIMP, a free image editing software removing first the outside wood floor with an erase brush, then using a combination of fuzzy select + color select to remove most of the white. Then a little cleanup with erase brush and I had a dungeon on transparent background.
This will definitely be the approach I use for my OPD entry this year, why not use all the bits and tiles I’ve painted up and crafted instead of my mediocre map drawing abilities?