Our old standby is little blini, warmed under the grill, topped with a dollop of creme fraiche and then either some smoked salmon, some caviare (just the supermarket stuff is fine) or both. You can just set out the pots of creme fraiche and caviare and a pile of warm blini and let people make their own.
Fry a load of minced onions and bacon till brown and caramelised, mix with any combination of sour cream/creme fraiche/greek yoghurt, salt and pepper, chill if you want or eat warm. Eat with chips or cut-up veg.
Store-bought puff pastry, cut in strips, twisted up with cheese, olive tapenade, or sun-dried tomato paste. Lay on foil on a baking tray and bake till brown and crispy.
Rosemary chili nuts (pecans or cashews are lush but any mixed nuts will work): sautee minced rosemary in melted butter, add dried chili flakes or chili powder. Add nuts and toss in the hot spiced butter and serve. If the nuts you use aren't salted, add some sea salt to taste.