Hm, for some more grown -up flavours, you could try:

(Let me know if you want recipes for any of them and I will post them)

- lemon yoghurt cakes (I'm sure they are called something much yummier, but they are great- greek yoghurt in them which gives this lovely tangy but sweet flavour combined with the lemon)
- banana passionfruit muffins
- honey ginger muffins
- hazelnut liqueur mud muffins
- raspberry yoghurt crumble muffins