I was wondering if cedar fenceboards would make a neat rustic wall for bedroom. But, do not want it to look unfinished.
As long as you have the ends trimmed neatly, I don't think it would. One thing I would keep in mind for this type board is the rough texture and the dust aspect. You might want to try and put a sealer on them. Are you thinking of putting up similar to ship lap or like a fence? I think that would also make a difference in the finish appearance. I would go with one accent wall rather than the entire room.
Only you can answer that...it's your opinion that matters! I would nail one board on the wall you plan on doing (at eye level or above since that's the area you'll be viewing most often) and leave it up for a few days to see it various natural light conditions. Then ask yourself if it pleases you. If it does, then proceed!
If you want a rustic look, I think this is a great idea. Ask yourself what finish you want. When I put shiplap up, I thought I was going to stain it. Then, I realized I wanted a lightet, brighter look, so I painted it a soft ivory. Eventually, I went lighter with white. I loved both, and was glad I committed to painting. It is much easier once you decide the finish you want. Cedar has a distinctive fragrance, so you want to consider if you want that or not. You could live with it for awhile, first. That was what I did. I would sand the planks before putting them up.
I got some decals from amazon.com and they look like different shades of barnwood. I took apart an old box spring and saved the wood from the frame. I cut to size and stained the wood and used that as a border to frame the barnwood decals. So just have the price of the decals and the stain since the wood was free. Then placed a metal ram cut out in the middle. Did all for less then $20 and it is original and turned an unused over looked area into a nice looking part of my hallway.
If you do use fence boards - make sure they are untreated. Pressure treated boards are not considered safe for interior use. :)
Might check the price of cedar closet lining boards, they are thinner and might be cheaper.... the bonus is they are smooth/finished. Cedar is the most expensive wood to use for a rustic wall.
Lowes now sells panels that look rustic! It's super cheap and huge! Here is a link for one.
I used it here in those post (as a backdrop for the bed I painted.)
I would suggest sanding them first for a more finished look. The brand Cedar Safe sells tounge and groove cedar planks that we used on a ceiling - https://www.charlestoncrafted.com/cedar-ceiling/