Custom image mapping using image URLs collected via gravity form

Hi,

I have a multi page Gravity Form (hosted outside of wordpress), that submits data via GF REST API, and users upload multiple images via a custom image uploader (files are uploaded to Wordpress REST API /media endpoint)

The uploaded file names / URLs are then stored into hidden text fields in the gravity form.
e.g. input_12 = https://<wordpress-site>/wp-content/uploads/2022/05/photo1.jpg

Once the form is submitted, is it possible to have these images merged into the PDF?

Previously when we had a basic form using standard GF single file upload, we could map this to an image in the PDF like = {photo:11}
And if we had standard GF multi file upload, we could map using something like this (to grab first multi file)
[e2pdf-format-output explode_filter="array_filter,array_values" explode="," output="{0}"]{:2153},{:2156},{:2157}[/e2pdf-format-output]

Now that we instead have an image URL in a text input (like input_12), how can we map this as an image in the PDF template?
Would {:12} work?
Or do we need some custom mapping, perhaps using e2pdf-format-output, to format the output as an html img URL?

Thanks