What an awesome Auntie! I love the idea of this. I know it sounds really simple....but what about an ornament every Christmas? We did this for our oldest son and will be doing it now for our new lil guy. Of course, the first few years we picked them out ourselves. But now that our son is a little older, he picks his own out. We go to a place in the mall (the ONLY time I'm caught in a mall at Christmas LOL) and they have those ornaments that you can write the childs name on them and the year. My son's tend to reflect on what he was in to that year or what was important to him....
1st Chistmas.....Obviously a 1st Christmas ornament
2nd Christmas.....a tricycle (he was just learning how to ride one by then)
3rd Christmas.....a guitar shaped ornament (he was very into playing Guitar Hero that year with daddy)
4th Christams.....Spongebob ornament. He loved that stupid yellow sponge.
5th Christmas....I'm a big brother (we were pregnant at the time with #2)
You get the idea......you could technically even just use the ornament as her gift tag (so its not the only thing you buy her....I know THAT temptation LOL)
Seriously, these ornaments mean SO much to me and HE also looks forward to picking out his special ornament now that he's older. This could be something special you take your neice out to do every yr when she gets a little older (like probably by next yr). Check your local mall....they usually set up these little shops right near where Santa is.....