I think I'd go for anything but Sarah. Jareth is low on my list but if he were done extremely well, I don't think I could refuse. Labyrinth means a lot to me.
Scale is dependent on who and how many. If it's a one-off, it'll be whatever best fits that character. If it's a line, then it'll be tricky to manage. I love the idea of a 1:3 Hoggle but a 1:3 Ludo? No thanks.
There's so many minor characters I would love to see but they're not viable as one-offs or to begin a line with. Top of the list is The Worm