Sharon, that's a wonderful idea! That is definitely a thing. People do dwarf shrubs, fairy doors at the base of a tree, a water feature, whatever is of interest. Your mini garden doesn't have to be similar to anyone else's, or you could like someone else's so much that you try to copy it. One of mine has a car junkyard in it, which was sort of a stolen idea from a mini that I saw where the whole thing was a micro junkyard.
I have an area where I propagate and keep a few mini plants but I get just enough fallen leaves that it's difficult to do much with the smallest plants "out in the wild."
