Can I put ship lap on one of my bedroom walls instead of a headboard?

yes; go to pinterest.com and you will find ideas and also youtube.com has step by step instructions!

http://weekendcraft.com/journal/how-to-make-a-shiplap-headboard

https://www.tableandhearth.com/2015/09/easy-diy-shiplap-wall.html

http://www.hgtv.com/shows/fixer-upper/fixer-upper-style--shiplap-decorating-ideas-pictures

I hope these will help you with your decision of whether to do an accent wall, headboard, or all of the room walls.

Yes, you can do anything you like as far as shiplap is concerned since it's your home. :) Regarding painting, I've only seen stained or white shiplap but you could paint it as a statement wall in any color you like. One thing that I have read is to paint behind the installation first so that there is color in the gaps. You don't have to paint the whole wall, just where the gaps will be. You could paint it first, but remember you're going to nailing it to the wall and you'll have those nail holes to fill and paint after you're done. I hope this helps. Wishing you the best.

Hi, we installed pine tongue and groove at our cottage. On a warm sunny day, I painted the pieces before they were installed - it's much less messier. I just put a vinyl table cloth on my patio table and used 4 saw horses. They dried very quickly. In the photo below, we hadn't yet filled the nots with latex filler. There are OSB boards behind the pine tongue and groove - I didn't paint those. Good luck with your project!

One wall, the wall behind the bed only.