In theory I made these with my kids year before last but I thought they looked really nice. Basically, a load of their splodgy paintings (the ones they do when they don't paint stuff just chuck the paint around) cut into Christmas tree shapes and then stuck on folded card with a little gold star on top.
We ran out of paintings to cut up so I started making my own!
with coloured paper, pva glue and glitter. Like tinsely trees. With nice card/paper and envelopes they would have looked quite grown up I think.
That's about my level of card making though!