As for flavors, I usually do that with final sweetening. Pineapple concentrate and Ribena blackcurrant syrup are both really nice.
Also, related is doing a simple apple ale. I add a bit of Malt to the juice (4/1 ratio) and then dry hop for 2-3 days when done. It makes a very nice appley beer blend taste. Still mostly cider, but certainly definitely a different taste to regular cider.