I had fun building a realistic barn, took me about a week's worth of planning and fine-tuning of the design. I especially like the details of the windows that big barns usually have near the top, and the storage and livestock areas i built inside.

Resource Pack: OR Textures (Operation Realism Official server pack)
http://www.operationrealism.us/downloads.html

Trees (by Smop95): http://www.planetminecraft.com/project/trees-amp-plants-of-the-southwest/

Schematic Available; may be used on a server only, please give credit