I have created my own dnd world and i have a lot of the basics down like religion, cities, heroes, and some more things. But now i am looking for other things to add just wondering if anyone has an ideas that would be fun or interesting for a homebrew world. Thanks much

What's more fun and interesting than a hero?

A VILLAIN!  Mwahaha! 

Try to add other planes of existence that are more unique and aren't just the basic ones.

Leaving yourself room to expand is always a good idea; recall that basically all of the Elderscrolls games take place on a single continent; there's always room to expand beyond that, or have things show up from "mysterious foreign lands" etc.  It's honestly a pretty useful asset to have from a writing perspective to have that part of your map that says "here thar be monsters"; it's part of why Star Wars had the "unknown regions" for so long; it's just a catch-all for any weird idea that a crerator might ahve that doesn't necessarily fit in the rest of the setting.

Whenever I DM I try to make completely new planes of existence because most of my players are experienced enough that they know all of the default planes and are way more knowledgeable than their characters should be.

In broad strokes, what have you got for your world that makes it your own world?

I started by making some ideas for one place in the world - I picked the biggest, most central place - and then I expanded on how that place has affected the area around it. Then I take each thing it created, and ask the same question.

For example - a market city which trades in everything. This will need trade routes to and from, which in turn will need safe places at a days ride apart, which in turn will cause bandits to pick places which are between, which in turn will make those safe places more fortified when near bandit territory, which in turn led the bandits to train a species of giant lizard to scale the walls, and so on. Fast track your way through an arms race in any conflicts to make things interesting - 2 people hitting each other, one builds a wall, the other builds a ladder, so one builds a moat, so the other builds a boat with a ladder, so the other gets people to shoot at the boat ladders, so the other blocks trade, so the first finds a route through the underdark for trade, so the Duergar attack, so they build a wall on their trade route, and so on. Making logical reasons for things to exist is a great way to keep things feeling less "it works because magic" and stops players from breaking immersion by saying "why didn't they just travel above ground?", as you'll have an answer.

Take things you want (EG a heavily guarded subway system through the underdark) and steer the logic towards it. What would make someone make it? avoiding things above ground. So what are they avoiding? and so on.

Two of the options you have for making your world completely different are adding or removign things. Perhaps the gods of war died in a war among the gods, and the more level headed gods decided never to replace them. You'd have a lack of fanatical warriors, and a more peaceful world, with people fighting for reasons and not "because it is our religeon!". Alternatively, if you added a god of Peace who was inredibly powerful, it might cause wars to go towards subterfuge and espionage, as the god of peace is vengeful to those who actively fight one another.

My big favourite for writing is History. The reason the world ended up the way it is. Anyone can say "there is a floating mountain castle which floats ominously around, smiting people with lightning", and it will be a cool idea, but what brings it to life is when you know exactly how and why it came to be, and the world around it matches. There is a huge lake where the mountain used to be. There are lost cities which have been smited in the past. There are legends and folklore of this great destroyer, sayings people use to frighten kids or superstitiously when they are afraid or needing luck. 

If you throw us some of the broad strokes of your world (what it's like, is it mountains or islands or bubbles on the surface of a huge bowl of washing up?) we can offer more tailored ideas!