Next time they say something like this, respond with something like "if I'm dating someone, I'll let you know. If you continue to assume things about my friends, or comment on their appearance, I'm going to stop sending you pictures."
If you introduce your next girlfriend to them and they don't seem to care, have an explicit sit-down conversation about it. Tell them how it makes you feel, point out the inconsistency, and tell them you're going to stop introducing them if their behavior doesn't change