You could cut leaf, petal, or feather shapes out of plastic lids or bottles and layer them like shingles. You could glue artificial flowers and leaves to a plastic take out food top or bottom...with maybe a glass paperweight in the center to keep it on. You could pour plaster with some tan paint into a pie pan, un-mold it, quickly rake from the center to the edges on the bottom with an old fork and set it upside down on top of your block - to look like mini thatch. Or you could use concrete patch instead of plaster, let it set longer, and put it on when cured. At that point moss or algae might grow on it if it's a damp location.