I LOVE doing stockings and collect bits throughout the year. Actually I think I may have about 2-3 years' worth of bits stored up
I hate plastic tat so always try to get nice useful things. But I don't really believe in giving toothpaste and brushes and pants - I strongly think stockings should be for fun play stuff and interesting things!
This year DD (6) will be getting:
- silk daisy chain daisies (National Trust shop)
- metal compass (also National Trust)
- mini binoculars (free from...National Trust
)
- small game - this year it's Sussed (from Amazon)
- mini sequin notebook and pencil (Tiger)
- house-shaped pencil sharpener (Rex London)
- cat shaped ruler (Rex London)
- hair bobbles (Rockahula, in John Lewis sale)
- soap in mini tin with cats on it (TK Maxx)
- light-up yo-yo (Ripley's, from House of Marbles I think)
- CD case of miniature coloured pencils (Paperchase)
- book (Allan Ahlberg, The Impossible Cat)
- mini penguin soft toy (White Company sale)
- satsuma
- selected choc/sweet things - a Lindt Santa, candy cane, tube of jelly tots, a Maltesers reindeer.
I normally put in - something for the bath, something that lights up, a game or toy, a book, a mini soft toy, hair things, pencil or pen, something sciency they won't expect. And always the satsuma 
In previous years DD has had: light up bath ducks, a proper harmonica, a mini kaleidoscope, a bug viewer, loads of pencils/crayons/notebooks, sticky markers, a mini crown on a headband, a purse, a wooden insect eye, mini soft toys, bath bombs, bath crayons, bath crystals, mini Lego packs, a skipping rope, Christmas slipper socks, seeds, stickers, a paper laser, bead bracelet kits, a mini butterfly kite, and tons of stuff from Tiger iirc....
For sweet things I rotate it between Lindt stuff, a Kinder mini Haus, candy cane or lollipop, tube of sweets/smarties/buttons, choc coins. When DD was about 2-3 we had much success with those cartons of vegan chocolate milk stuff which she loves. And occasionally I slip in a nutella and breadstick pot. Father Christmas knows nothing of Palm Oil.