I've worked with all kinds of art mediums, in all kinds of scales, but the medium I always go back to is paper. You can do such a range of wonderful things with any type of paper. As an example, just look at the wonderful work of Cheong-ah Hwnag, paper sculptor, on her website Papernoodle. From birds, to plants and architecture, she does it all. And a lot of what she does would be considered 'miniatures'.
If you could only take one type of material with you to a desert island, what would it be? Would you work larger or smaller than you do now? What is it about your chosen material that lends itself to unlimited experimentation (assuming that's why you take it with you to the desert island!)?
Some of the paper miniatures on this site are printable miniatures, but there are other paper based project, including the miniature plants which are so much more realistic made from paper than from polymer clay or fabric. I'll have to come up with some cut paper background projects for scenes, and some paper based furniture projects. Stay tuned!