Cool project, as @Acliff noted dark wall paper will be a bit gloomy.
I'd really recommend lighter colours with a good amount of reflectance (matt white is around 80%). It doesn't matter how much output your lighting has if it's projecting onto dark surfaces. Also worth thinking about the lightness of your desk finish, this will work as a reflector and put light onto the (hopefully white) ceiling from any downlight. I've not seen the IKEA light panel but you might want to try different positions before committing. Directly above you will give most light onto the task surface but if it's in your eye line may become glarey and the ceiling around it may look dull. I'd probably be looking to mount it on a vertical surface that isn't in my eye line and doesn't reflect onto my screen. That'll put light everywhere and a bright ceiling equals greater perceived brightness.
PS, if you need task light for any non IT stuff, sketching etc I'd recommend a desk light.