What color has she painted the room for the twins? That's always my big clue as to what the mother will like in the color ranges. There are lots of gender non-specific themes for babies. Alphabet blocks, numbers, teddy bears, nursery rhymes. The pages for soft baby books make great blocks. Baby animals make another great way to go. I personally hate to see a baby wrapped in a quilt that looks like it was pulled off of a sofa. I like a baby quilt to say baby in one way or another since babys are so special and happen so infrequently. Your niece will probably only have twin babies once in her life.