I did a slideshow for a bar mitzvah using childhood photos to make up a larger image of the kid playing la crosse. I used a program called Shape collage that I bought fairly cheaply online to make the collage, and then used the "overlay" transfer mode to lay the mosaic over the final image, or logo in your case.
There is a replicator internally in Motion, and you can import an image sequence (multiple images with files names of at least 3 digits in sequential order) Just select the random start frame checkbox and adjust the parameters to arrange and move the images. You can also use transfer modes to show through the mosaic to reveal your logo this way.
Hope that helps or at least gives you some ideas!
You can create it with MacOSaiX but difficult to then break it up in Motion without jumping through a lot o hoops (you need to use a process Patrick Sheffield shows in his Motion book). In After Effects its easy to break up and animate using the Shatter effect. No such effect in Motion unfortunately.
Freelance Producer/Editor/Motion Graphics Artist
Apple-certified Master Trainer
Author, Motion 4 from Peachpit Press http://www.applemotion.net