This is what I used at my wedding. (The waiters mixed it up in a big new clean garbage bin!).

3 part sunshine punch fruit juice (comes in a big time at supermarket)
1 part ginger ale
1 part lemonade
+ diced fruit and lemon and mint for colour.

Not very exciting though but yummy.

Another unusual punch is partially frozen crushed pineapple (slushy consistency) mixed with equal part cola. It sort of sits in two layers. If it combines it becomes a nasty browny colour but still tastes good. Try it and you'll be suprised!