For my DD I sometimes group little bits of things together and make cellophane parcels to put in her stocking - look a bit more special and expensive than the tat things really were.
So you could add to the nail varnish thing - as someone else said, magnetic nailvarnish, or does she have any crackle top coat? My DD loves that. Plus some quick-dry spray, topcoat/base coat, sparkly emery boards/nail corrector pens
Craft items - blank cards/envelopes; stickers/toppers; peel offs (usually "thank you" ones for my DD as an unsubtle hint, but also happy birthday etc)
Cake decorations/cookie cutters/writing icing/cupcake stuff
Other things my DD has had over the last few years:
Things she needs - tights, socks, knickers, toiletries, hairbrush, hat, scarf, gloves
Puzzle books - suduko, wordsearch, crosswords
Purse; key ring; mobile phone charm; jewellery/badges/
Cinema vouchers and popcorn (given that we were planning on going to the cinema anyway!)