Facebook offers an application that can turn any photo in your account into a mosaic. The Profile Photo Mosaic app is free, but you do need to have the photos uploaded to your account before attempting to use it. Once complete, the mosaic photo will appear directly on your Facebook wall. Anyone who is friends with you will be able to view this photo. From there, you can add it to an album or make it your profile picture.
Log in to your Facebook account with your email address and password. Search for "Profile Photo Mosaic" in the search box at the top of the screen.
Click "Go to App" on the screen. A box will appear to launch the application. Click "Allow" so the application can access your Facebook profile.
Choose the photo you wish to make into a mosaic from your albums. Click "Create." The program will publish the result to your Facebook wall.