Split the croissants open sandwich-style but not all the way, so they have a hinge at the back. Spoon in 1 tablespoon of seafood salad, then tuck 1 or 2 baby spinach leaves underneath. Insert 2 toothpicks into the top middle of each croissant and press a caper onto the point of each toothpick for crab eyes. To make crab claws, cut the grape tomatoes open from bottom end to stem end but not all the way, leaving them hinged. Stick a toothpick into each tomato at the stem end, then insert a toothpick with a tomato into the point of each end of each croissant. Arrange them on a serving plate.