Welcome to MR!
That functionality is already available...you just need to do a little manual work first
- Add all the images to Sigil using "Add Existing Files"...hopefully you have them named appropriately so they show up in the proper order: eg. img-001, img-002, etc.
- Run the plugin - you should see all your images in the select image window
- Select the first image in 'Select image'
- Select 'At the end' in 'Select position' dropdown
- push the 'Insert' Button (nothing will happen! It's OK)
- Select the next Image in 'Select image'
- push the 'Insert' Button (nothing will happen! It's OK)
- repeat the previous two steps until you are done with the images you want to insert
- push 'Close' button when done
All the images will be inserted: 1 per-page
I'm not sure if there is an upper limit to how many images you can do at once...I'd probably do 10 at a time to begin with....