It's funny you mention that. I just bought that game for the Wii and noticed the trees. But they are much different in style. Super Paper Mario Tree.
(P.S. The game sucks and the story is long and obnoxious.)
It happened midway through the Lighthouse design. I had the outline and layout all set up but the water and sky looked bland so I had to do something to it. The challenge only had 8 colors and I'm not a pro at dithering. So I decided I put the pencil at 2 and squared it all off. It still didnt look right so I did some tricks to make it more varied and imply distance.
I'm pretty improvisational when I'm making art, so it just kinda came on its own. Thanks for comments everyone! I'm happy I found a cool new style for myself!
Its kinda lame but... Still it some how looks cool :D Nice work!