I’ve only skimmed the package and its dependencies.

My suggestions:

If your src-attributes contain relative or absolute pathes to the pictures you will probably need to save them on appropriate places relative to the workingdir of wkhtmltopdf, but I can’t tell you were that will be.

Another possibility might be to use fully qualified src-pathes, including schema and host. Then wkhtml should do HTTP(S) requests to your server and fetch files as necessary. But these are blind guesses, I do not use that library (or any PDF generator as well).

Also please take a look at gutschilla/elixir-pdf-generator#19 and gutschilla/elixir-pdf-generator#20, both could give some lights on this, even though 20 seems to be still untouched after 8 months…