Legally, if the pictures are not being posted for personal gain and are in public locations, and the pictures do not harass, libel, or disclose personal facts, legally, your ex probably cannot prevent it.
Now, my bigger question -- why do it? By posting about an ex, you may be inviting a host of problems. You risk a harassment or defamation charge or lawsuit against you, and, at best, you may look bad in front of strangers. Moreover, while a lawsuit or criminal claim by your ex might not be successful, that doesn't stop the complaint from being filed. The only action that prevents a claim is by not "going there" in the first place. Finally, once it's posted, it's out there forever... it's like hitting "reply all" to the universe. It can only be damaging.
In short, discretion is the better part of valor here; don't post anything related to exes and take down anything objectionable. It's not worth the fight. Good luck.
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There are a couple parts to this. 1. Pictures - as long as the pictures are tasteful, NOT NUDE, NOT SUGGESTIVE, NOT PARTIALLY NUDE, it is very likely that you have done nothing wrong in Maryland, either in the taking of the pictures, or in posting them. I agree with the earlier commenter that it is a bad idea to post them if your goal is to annoy, harass, embarrass, or disparage your ex-girlfriend in any way. At some point, your actions become criminal, but I haven't heard anything in the description - regarding the photos - that constitutes criminal activity yet. Civilly, you could be liable if they are defamatory. Any lawyer would need a LOT more information to say.
2. Video - This is a danger Will Robinson, danger moment. Maryland has one of the more broad wiretapping statutes. It is a 2-party consent state. If this VIDEO has audio capability you could very easily run afoul of the law just having taken it. Nothing in your description says she consented to your taping. I don't even want to get into the posting of the video. Taking it sounds like it might be problem enough on its own.
Every legal situation is different, and this answer should not be construed to apply to all cases. Contacting a lawyer about your particular situation is always best. A decision to rely on this answer in making decisions about a case establishes no attorney - client relationship.