Thank you for getting in touch with us.
In answer to your query, yes, you are able to add your Royal Mail PPI Images to Expandly. These can then be added to your Invoice Template, which you can then use to print labels via your Manage Sales Orders page on Expandly.
I have attached a Support Guide below which will help you with adding these to Expandly:
I hope this helps - If you have any further queries, please get back in touch and we will be happy to assist your further.
Have a great day!