This is a paid asset, but now you can download Photo Mosaic Free.
Detail this asset from Unity Store: Original Link
Photo Mosaic v1.0 (Latest version)
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Photo Mosaic is a library for you to real time create photographic mosaic, and it’s mobile friendly. Photographic Mosaic is a visual effect that tiling images to form a one big image. We get two methods for you to do this effect, group of MeshRenderer, and Image Effect. Each suits different situation, so that you can try more possibilities or visual creation. The library also allows you to load photos on run time, or create photo dataset before play. PS. Because it’s real time, it can handle <256 images for one effect