The" one-bite party-snack" contest may have some ideas for you: http://food52.com/contests...
Generally, anything on a skewer or toothpick, on a crostini (there's a carrot finalist from the party snack contest) or in a pastry cup. A cheese plate also always works well. Depending on what else you're serving, you might opt for oysters on the half shall. Other ideas include: cold soup shooters, dried fruit stuffed with cheese or wrapped in bacon (there's a bacon wrapped apricot from the party-snack contest, which looks great), scooped out baby potatoes stuffed with _____, and tartelettes. From the previously mentioned contest, I'd also check out the herbed biscuit with ricotta and the chestnut cracker with caramelized onions. Both looked swell to me.
P.S. Placing proteins and vegetables on toothpicks or on platters with toothpicks often makes it easier to ensure there's variety, as opposed to having everything served on a carb.
Following the Spanish flavor - you could toast thin baguette slices and top them with a piece of Manchego cheese and a bit of membrillo (quince paste; also delicious made with pears.) Both should be available at any good cheese shop. Would go great with the sangria.
Almost forgot - kind of trendy lately, but Spanish Marcona almonds really are great with drinks, especially wine. They can be a bit pricey, but Trader Joe's has them toasted with a relatively reasonable price tag.
Lots of tapas type dishes would suit your needs. I assume toothpicks are okay?
A platter of marinated roasted pepper strips with garlic and capers, (anchovies) to be forked onto toasted baguette slices.
Tiny meatballs in saffron sauce.
Roast asparagus, if you can get any
Melon slices wrapped in prosciutto
Shot glasses of gazpacho
I like Roquefort Grapes from Martha's Hors d'ouvres book. This would be great with snagria. A perfect bite and it is not messy because it is rolled in nuts. 8 oz cream cheese, room temp; 4 oz Roquefort, room temp; 2 Tbsp heavy cream; 10 oz almonds, pecans or walnuts; 1 lb, about 48, red or green seedless grapes.
Toast the nuts, chop and set aside. Cream together the cheeses and cream in a large bowl. Drop the grapes into the mixture and stir well to coat. Working with one at a time, fish out a grape from the mix, forming a ball and roll in the nuts until well coated.
I made all these plus a few more things for a party.
I always serve fried chickpeas and they go over really well! Just cook some chickpeas (out of the can is fine too) and dry them well. Heat up about a quarter inch of oil in a pan. The oil is hot enough when it starts to bubble around one chickpea. Fry them until they are crispy and then spoon them out of the oil with a slotted spoon and drain on paper towels. While they're still hot toss with whatever seasoning you like. I usually do smoked paprika, chile powder and salt.
This is obvious, but I really like good potato chips at parties. Whatever the brand is that does "salt and black pepper" flavor. They are delicious, great with all alcohol, and easy to prepare. I also sometimes do Thai heavenly/sundried beef (basically a homemade, coriander-crusted jerky) when Thai won't clash.