I don't think they are morbid. I think it is lovely the remember someone with an ornament. Maybe it feels weird with the date or verse on it...so why not just use a picture ornament?
My sister tragically lost her husband three years ago. He was big into Christmas and decorating with lights. So every Christmas so far she and my neice go and decorate his grave with a little tree and even some lights. Someone once said something to her that it was tacky or something like that but knowing Mike he would have LOvED the idea.
When it comes to how you remember your loved ones I think you should follow your heart.