These are my ideas i hope you like

1. Customizable backpacks.

2. 50% chance that mob heads drop when killed

3. Treasure maps that show abandoned mineshafts

4. Ability to combine customized banners with beds

5. A really rare biome that has natural spring water that gives 20 hearts for one day. The extra 10 hearts wouldn't regenerate after damage. 

6. Customizable capes

7. Land claims

8. Trading station

9. A block that's used for selling that people can't steal from.It holds a creative inventory that you can click an item to pay for. 

10. Caves full of ores mostly diamonds. Ultra rare, one in a million chance. Called the Good Stuf Cave.

11. Tamable whales.