Hello @Manx17 and thanks for reaching out to Ubisoft Support.
I am sorry to hear that some of decorative elements are missing. In order to investigate it further we need to know the names of missing elements (you've mentioned you might be missing more than one). Please also provide some screenshots showing that the unlocking conditions are met.
Note that they can be a maximum of 2,000 pixels in length, 2,000 pixels in height, or 2MB in filesize. Alternatively, they can be uploaded to any other website of your choice, and a link sent to us here on the forum thread.
We look forward to hearing back from you.