Yes. after all, a client that recognises the kind will probably have some sort of custom render. a client that doesn't should print the alt tag.
I'm not sure about including the gitworkshop url.
I don't think it is good for the UX when clients hard code links back to their own client. May be its ok there are so few nip34 specialised clients.
I really like the 'Open in' based on client recommendations from my WoT. There is a NIP for that right?