You could play around with the tiles... some trunk pieces can look like wooden walls, some floor tiles like bricks or ceilings. You can always do some editing and cut some pieces...

Just be careful when you find something, that it is properly licensed for the contest

I was also curious why there is such a lack in creatures / mobs / animal sprites?

Would love to see more of those,

but all in all this LPC is a great resource for amuteur game programmers like myself and thanks for that.