Oooh, a ball! Sounds like you want to be posh.
A plate of asparagus spears / bread sticks / two or three cooked but chillled tiny green beans wrapped in parma ham
Something served with salsa verde for dipping (salsa verde = lots of parsley, half the amount of mint, some dijon mustard, lemon, anchovies, capers, salt and pepper whizzed up). You could try tiny new potatoes that you've roasted; slivers of cold rare roast beef or poached chicken.
miniature corn and ricotta fritters (eggs, ricotta, flour, sweetcorn, lots of black pepper, a dash of milk, plus maybe a touch of chilli powder) plus shop bought sweet chilli sauce for dipping.
Chicken ceasar salad mix served on dollops on little gem lettuce leaves with a peeling of parmesan.
Most of this you can do in advance and heat up as necessary (fritters, potatoes). Whatever you do you need to make sure there is some balast so people don't get too pissed beforehand.