You should be able to. Just select another photo/video from your gallery (the same way you selected the first) and you should see a carousel of the photos/videos youโre about to post.
Discussion
I can do that. Choose a photo, upload it, choose a photo, upload it, and then see the carousel of photos Iโm about to post. But I was thinking more of being able to select multiple photos (like my screenshot example), upload them all at once, and then see them all before I post. Instead of being asked โare you sure you want to upload this media?โ after each photo I choose. 
I havenโt seen the ability to upload multiples at one time yet, either. Iโm still uploading one at a time.