What are some good sensory development activites for (learning to crawl) infants?

I work with a just turned one year old.
I’m with him 45 hours a week, and I’m having problems figuring out some good sensory activities to do with him.

He has Down Syndrome which is a lot higher functioning than the kids I am used to.

He’s learning to crawl and actually crawled through three rooms in a row today! and feed himself, so we have been working on that a lot for the past two weeks.

I have been bringing my sister’s sensory box different textured fabrics/brushes, colored things to sort, etc. over, and he seems to really enjoy the time we spend exploring what’s in the box. He really enjoys being read and sung to, as well.

Do any of you have any suggestions on what else I can do with him to help improve his sensory development?

If this question makes no sense at all, I apologize. I’m multitasking.