My mother (93) says she sees my father's images on the walls. What do I say?

Ask her what he is doing, what is he saying. If the hallucination is pleasant, go along with it.

I agree with the others but you could als say that she must miss him terribly. Ask her what it's like to see him. What he says to her.How it feels to see him. What is her favorite memory with him. Get her talking. Sometimes it's a coping skill.

My mom, who just passed recently, kept saying she was seeing babies, so I would sometimes be walking through the living room and she'd gasp, saying,'Oooh, you almost stepped on her/him!'
I finally started joking with her, saying,'You know, we really oughtta do something about these people leaving all these babies laying around!'
That kind of diverted the attention to the fact that she was seeing things, while not telling her that she was.
But sometimes it was creepy when she would point next to me and say that this one must like me cuz its smiling at me.
Just humor the occurence, while not patronizing the person.

Probably the best thing to do is just agree with your Mom as if you say you don't see the images then that would upset her even more.

My experience was a little different in that at times Mom thought I was my Dad...and he passed in 1975. It was upsetting at first but I dealt with it by just going along and answering her questions as if I were him. If that made her happy it was ok with me. Not easy for me...none of this is...but that appear worked.

I agree with going along with hallucinations and delusions, unless they are painful to the person having them.

I don't agree that seeing a loved one is a sign the end is near. My husband saw his late brother very early in the disease, about 10 years before he died. That is because in the progression of the kind of dementia he had, hallucinations typically come first. When a person sees loved ones from his past probably depends a lot on how the dementia is progressing. It could be any time.

TOTALLY validate what she sees!! Depending on your relationship with mom, heres a few ideas that might get you thinking of some snappy comebacks. "isnt it nice to see dads face everyday?, I find it comforting.", or more humorously, "yeh mom, isnt that neat,? do you know what it wouldve cost us to have his image printed up? dad gave us a freebie!" or "He loves you so much he is still keeping an eye on you, isnt that comforting/deep love?." Or "til death do us part was part of your vows, guess he kept his word and isnt going anywhere yet.", "I hope I have someone that still loves me enough to stick around when Im 93".....

If its not comforting, offer to place something else on the wall(s) where she sees the image.After 23 years, I dont think the images are going anywhere, so the old expression "if you cant beat em, join em" might offer you some comfort.
My mom would bring things up that she was in disagreement with my dad over (several years after he passed). The first time I said hes dead and that did nothing to help the discussion. The next time I presented a logical counter argument that he would have made in as close to his words as I could come up with, and she finally gave up the topic after being reminded ("remember dad said...") a few times that day. The more it sounded like dads words, the more comforted she became.....
Does she have memory deficits or is shes "ok" other than seeing dad's images?

Agree! He's there, isn't he?!!

Added on...my Dad started seeing my mom, talking about her more and saying he was at appointments with her about five months before he died.

My mom had Lewy Body dementia and 'saw' lots of people from the past, or at least swore they were living in the house, unseen. If the back bedroom door was ever shut, she said people from work were sleeping there, or my brother, or her parents, or even people on tv. Just smile and nod, change the subject. No use arguing. Even if you can get them to agree 'dad' died years ago, he will still show up again.