Found it now (hint for others: check Johnny's twitter), but didn't seem to do much. Any other new secrets in the demo? (Great demo BTW, real standout from the Haunted PS1 scene)
In the dark area with all the eyes (sorry I can't think of a better way to describe it), there is a window with eyes in it that you can jump up to and go through the window into a secret area with a spot where you can plant the sprout, but I haven't anything new after that. Hope that helps, and if you find anything else new let me know.