All basic collages - the ones where you can set your own layout - will now be available in this new largest size on canvas. For designer collage templates, the available sizes depend on the specific design. You can look up the available size options for the design you want in the collage creator.
Want to make a collage right away? Start up the collage creator.
Update September 19th, 2012: collages are now available up to 150 x 100 cm.