This is Elias with Shopify Support. Thank you for reaching out.
While there are many bulk actions available on Shopify, I'm afraid bulk importing images isn't one of them at this time. Our guide on uploading images does cover some of the limitations and best practices when uploading images. When creating products, you can drag and drop media files multiple images; however, this isn't available on blog posts as well.
I can see how bulk importing images can be beneficial for our merchants, like yourself, and I'd be happy to share this feedback with our teams. Though this is not something that I can provide a timeline - If Shopify moves forward with this feature, you can find it on our changelog and announcements page.
That being said, how many photos are you uploading to this blog?
Thank you for following up!
Alternatively, there are a few third-party image slider apps that can install a slideshow to your blog posts. For example, Enorm Image Slider & POWR Image Slider & Carousel offers a variety of sliders that you can put on any page of your store, from hero sliders (slideshow) to carousels and much more. If you need help with one of these apps, you can always reach out to the developers through the contact information found in the Support section of their app pages.
Let me know if this is what you're looking for?