BrickLink has rolled out the open beta for their newest feature called Mosaick. It is basically a tool to allow anyone to turn an image into a digital LEGO mosaic. This also allows users to adjust resolution and size to their preference and price points.
After you upload an image, Mosaick gives you a number of options for shape, size (5x5in.-60x60in.), color, and part type (plate, tile, brick). It also gives you an estimated price as well as a parts list to show which elements are need to recreate a particular image. I did a mosaic of my logo to see how it looks and it seems to be running pretty smoothly.