i made a couple of these and your imagination can really help you make yours the way you want it to be. basically, i pretended a tree branch was a bike frame then filled in the rest with bike parts. but i put a tabletop instead of a seat. the video shows how i made it.
i apologize that this isn't a traditional "instructable-style" write-up; i make these videos for my youtube channel and try to share them here as well, for anyone who may be interested. this is a build for someone who would consider themselves "proficient" or higher with woodworking. feel free to ask questions and i will do my best to answer.