[Faceman]

My stalker-party was one of my favourite ones
I'd suggest
PC
Valygar - another stalker and one of the best tanks in the game
Keldorn - for his Inquisitor abilities (True Sight and Dispel Magic)
Mazzy - for her interactions with Keldorn and Valygar and because with a short bow she's the only ranged backup you need (Tugian, later on Gesen)
Jaheira - most versatile; for healing, as a backup tank and for her fire elemental summonings early in the game; also the most extensive romance
Imoen - because as a Stalker you're good and because she's THE best good-aligned mage

Before picking up Immy, you could either take Yoshimo or Jan for thieving skills. Nalia would do as well, but a lot of potions would be in order for her.
Personally I'd take Jan, because you need some arcane magic and though Nalia is a great mage her thieving skills are ridicolous.