Re: Tiles for edging
If you don't want to reinstall tile baseboard, then fill the area with drywall and tape/texture it to match the plaster walls. Follow that with two coats of primer and two coats of paint.
Sabo's idea of wainscot isn't a half bad either, though you will still need to fill the hole left by the tile to give some backing for the wainscot and new baseboard. If you go this route, wainscot ranges from 32" to 36" from the floor, what will work best for you will depend on chair and/or window height within the area where the wainscot will be installed.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!