There is a fun material called, coloquially, 'Green Stuff,' which is amazing for sculpting on a very tiny scale. It is actually Epoxy Putty Tape. It comes in strips of blue and yellow, and when you mix the two components you get a green putty that can be mixed to your own preferences (how sticky it is) and hardens over roughly 24 hours. It is a great medium to work with for art. You can also use it for fixing things.
My first experiment with green stuff was this spider. It's just a green stuff spider on a rock, which I then painted with a fake gold leaf.
Becoming more ambitious, I made this Gollum, a la Lord of the Rings, who is on a barkchip rock. I use densitry tools and toothpicks for shaping the material.