Hello troyfromFW,
I understand photos assigned to some of your contacts do not appear in Messages on your Mac. I'd like to see if I can help you get this working as expected.
Regarding the contacts whose photos do not appear, did you manually add those photos to Contacts on your Mac or did they sync there automatically? Open one of those contacts in the Contacts app and then click on the photo. Underneath the photo it should tell you which type of account it's syncing with. Do they say 'iCloud' underneath them, or do they list another type of account?
Compare this with a contact card for someone whose photo does appear in Messages. Does it show the same account name under the photo? If there are multiple photos with different account names underneath them in the contact cards you're experiencing issues with, select the photo for one of the other account types and then select Done. Close out of Messages and Contacts and then reopen Messages and see if the photo now appears.
If all of your contact card photos have the same account type under them, even the contacts that aren't syncing a photo to Messages, try changing the photo on one of the contacts you're having issues with: Add or change contact pictures in Contacts on Mac. Close out of Messages and Contacts and then reopen Messages and check to see if the photo synced. Respond back if you continue to experience the same thing.
Thanks for using Apple Support Communities.
Take care.