The honour gained at lvl19 will buy you a Veteran's Toothbrush at lvl70, you could PvP for six months and barely afford a single piece of lvl70 gear. Honour gained increases with level.
I personally don't rate Shaman twinks as they can use most of the same gear as Rogues but to lesser effect, dont have Windfury, dont have any totems, and are usually outperformed by other classes, sadly.
But, if you're determined, I'm sure it will be good fun.