So I tried this and it worked great, but I had a lot of issues separating the logo bits out from the other layer 21 stuff (like some others have voiced).
At one point I tried putting it on layer 200 and just moving it as a group to layer 21 after I had it positioned, but that was a pain too.
So what I did is to create a library in Eagle, import the graphic into some packages (I have one each for .5, .75 and 1 scaling). Then I created a "created by..." (or blank probably works) schematic symbol and created devices for each logo size.
Now I can simply add the logo directly to the board from the library and move it around as a group from a single origin. Super easy!
Thanks for this instructable!