Well coming from customs & Big Dog motorcycles I have allot of contacts with custom stuff. One of the biggest pieces on your bike that cosmetically enhances your bike's look, is the seat. Figure it has just as much surface area as tins on your standard, non bagger, bike. But even on your baggers it's some major surface area.
If you are looking for exotic leathers, custom inlays, or embroidering. Scott at
Bad Ass Bike Seats knows how to stitch some of the best custom seats I have ever seen.
If you want custom hand tooled leather that is unbelievable to see. He does everything from seats, tool rolls, or grip wraps.
RMH Custom Leather is the place to go. Roger is a true artist.
There are few places that I endorse as much as these guys. Their sites don't even caption all the bike seats that I have seen of their work. And NO its not just on the web where I see their work. Scott is a fellow michigan rider and I have nearly a half dozen guys I ride with that have MHL seats, rolls, or grip wraps.
I can link the big dog site threads if you all want to see more of their work.
Custom Seats 
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