Without meaning to be awful what you are requesting is around 15-20 hours of solid drawing for a full detailed backpiece.

Coupled with that it may only be a possible tattoo as opposed to a definite one I cannot see any artists jumping to do that for free.

If you are serious about it I would recommend a portrait artist who will measure you up and with the way you have described I am sure could do a piece.

There are 2 ways you can do this;

You can go for a cartoon strip style with boxes and possibly word balloons showing each scene.

Or

You can go for a portrait without borders so that each section flows into the next and the viewer has to decipher the chain of events.

I would recommend if possible taking some pics of the charcaters to the artist so they can draw it up.

Eg 9I know these are from the film but there maybe books you can use)

http://www.losthighwayrecords.com/images/local/artists/33115bd1-85dd-43a2-9f2f-b93bb88bbfb5.jpg

http://www.timboucher.com/journal/wp-content/uploads/2007/12/o-brother-where-art-thou-2.jpg

Pay a deposit and get a pro artist to sketch it up.

If you decide you don’t want the tattoo at least you will have some great wall art.

Take Care
Matthew