Attach photo to message

Additionally, if you want to add a photo to an already started text message click join the button to the left of the text entry window and select Photos from the menu that drops down:

However, only thumbnails are sown and not albums to be sure to know the filename or title of the picture you want so you can search for it.

In Photos, select an image and choose File>Share>Messages.

Be Happy 😎

Glad to have helped.