Gotta admit that it took (and still takes) me some conscious effort to keep my looking at the instruments to a minimum. Don't know if that's really an FS-induced thing, though (with my new MSFS PC including TrackIR and a big flatscreen one can actually look "outside" quite well
), or rather my being leery of letting airspeed and altitude unchecked for some time, especially in maneuvring flight.
WRT wallpapers, to my knowledge several people actually hang cockpit posters at their walls for familiarisation and checklist flow practice (not so much for simple SEP aircraft, though).