We don't have a bulk photo upload yet.
But you can save all of your images in our Asset Library and you can use it anytime without the need for re-uploading.
Go to Publish Editor > Click Add Images > Click Upload An Image.
Repeat the process for all of your images.
When you do this, you are saving your images in the Asset Library.
So when you have to create a new post, you don't need to upload an image again, you just need to click on Add Images > Select the Image.