I’d definitely keep the picture rails if you are keeping other period features.Positives I find with them:
– Genuinely useful to hang picture from
– You can moved pictures around as you wish and don’t have to worry about filling in holes
– Painting the walls white above the rail feel like it increases the height of the room
– You can use different chains, ropes etc to hang picture lower off the hooks to add a bit of interest, it’s something people often comment on in my property
I’d suggest getting sets of hooks off ebay though as most DIY stores charge an absolute fortune for 1 set.
Good luck with the renovation.