I have to help create a logo that uses an aspen leaf.

I need a fairly high resolution image of one -maybe two megapixels or more.
Does anyone know of an image board or something like that where I might find one?
It can't be a copyrighted image or anything like that.

My usual google-detective skills have failed me -at least for an image that is in high resolution.

Any help would be HAWT, thanks.