Mosaics made out of LEGO can look awesome if properly prepared, but they're also fiddly and time-consuming. If you don't fancy inserting all those tiles onto a board yourself, a LEGO Mosaic printer can do the work for you. This video explains how to build your own.
JK Brickworks' LEGO Mosaic printer hits all the right Lego buttons. It prints LEGO mosaics entirely out of LEGO parts, right down to using a Mindstorms EV3 as the brains of the operation. The colour sensor from the EV3 is first used to scan whatever you want to make a mosaic of, while parts are sent to the printer via gravity feed.
In a multi-part YouTube series, Jason Allemann walks through the design and creation process. Now, where did I leave my big box of LEGO...?