Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Confusion; Situational Awareness; Troubleshooting; Workload
Ground Event / Encounter Ground Equipment Issue
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings; Airport; Environment - Non Weather Related
After landing [Runway] 16R; were given instructions to back taxi on [Runway] 16C to Taxiway M; and hold on [Taxiway] M. While there are taxiway signs when taxiing in that direction there is no plastic insert with a taxiway designation when you are taxiing northbound on [Runway] 16C. In fact; there are several locations where this exists all over the airport. I suspect it is due to times long ago when operations such as back taxiing did not occur; probably before the installation of [Runway] 16R. It is very challenging to see surface paint when there is any rain; let along moderate to heavy rain like this particular evening; illuminated signs would be very helpful.  It would be a nice safety project to add these taxiway signs to facilitate turning off at the right locations. Please add these signs for ease in determining where you are.
Air Carrier Captain reported there is a need for taxiway signage (plastic inserts) at SEA on Runway 16C northbound. Illuminated signs would be helpful on a rainy evening.