i love it when people put up a selection of photo's of their family in differnt frames, in black and white and colour mixed in with photo's of landscapes, or flowers and such, not to many as it will look cluttered, not to little or it will look to sparse
I agree with you, T&G pannelling sounds hideous. We have the same issue with stairs as you, wall on both sides and we've had them painted both a magnolia-type colour and a sort of pale stone colour. The stone colour was much better with a bunch of photos as cookielove suggested.
Agree T&G would be awful.. ours are similar by the sound of it, we have just decorated in a sort of light coffee colour with a shell lightshade and a roman blind in the window at the top. Am planning to do a display of photos and have a big mirror at the bottom which reflects light in from the front door.
How about getting rid of the carpet and sanding the stairs. Or if you don't have boards, or they're not in good condition, try painting them (Farrow and Ball do floor paints now, expect loads of others do too).
Also, how about a big mirror at the top of the stairs, and a selection of unusual shaped ones on the way up the stairs?
Family photos all up the stairs look lovely - i did it in my prev house - but if the stairs are narrow you will find that you re forever knocking them down. I painted 2 lines in a darks green up the stairs at dado height, intending to do a swirly art-deco design below (inspired by the staircase in the hoover biuling, Ithink it is) but it looked ok as it was, so left it.