Quote from CallMeCratersWhen I previewed the world in creative, I found a mineshaft towards the top left corner of the map and another one located at the bottom right portion of the world (below a forest biome). As for pumpkin patches, I've found a patch of 4 near the desert village on a nearby mountain. I also found a small patch near the top right corner of the world inside a forest biome that borders a jungle. You can also find pumpkin + melon seeds in the mineshafts.
Thanks for the info! Here's a gallery of some screenshots I took this morning if you want to throw any of these up there: http://mcxphotos.com/nic.swaner.54/tu12-seed-1575524070073114809