ImageGear provides the following mosaic effects:

• IG_FX_pixelate gives groups of pixels identical values, and optionally adds borders between these groups. The groups can have the shape of rectangle, rounded rectangle, or ellipse. This transform effectively reduces the resolution of the image, and can make it appear that you have zoomed in on a smaller image.
• IG_FX_mosaic_tiles creates a mosaic effect by dividing a bitmap into tiles of a specified shape and size, changing the color of all pixels in each tile to the average color of pixels within the tile, and adding 3D borders between the tiles.

See also IG_FX_pointillist in the Artistic Effects section.

Original	Pixelate Effect
Tile Mosaic Effect - Square	Tile Mosaic Effect - Spider's Web