The right birthday present can make your mother's 90th birthday a celebration to remember. A 90th birthday should be treated as something special. An older woman usually likes to hold on to her memories and talk about the fun she had and how things were in old times. She enjoys reminiscing. She would appreciate a thoughtful gift that will remind her of her family.
Before your mother's 90th birthday, spend extra time with her and ask her what she remembers about her family. Write down all the names she remembers, and the relationships to each other. Use genealogy sites on the Internet to verify the information she gave you and to fill in any gaps that she didn't know. Use this information to make a beautiful family tree. Purchase one that you fill in the names or make one of your own. Frame it to make it last forever and present it to her as a gift.
Legacy Photo Book
Make a scrapbook with pictures of your mother through the years. A 90-year-old mother has a lifetime of stories filled with rich experiences. Tell the story of her life with the scrapbook. Get everyone involved, including older family members. Ask them to mail pictures to you and to include short notes about their memories with your mother that you can include in the scrapbook. Plan this gift far in advance and it will be a gift she treasures.
Another option would be to take the all the photos you have collected and bring them to a store that makes photo books. Photo books are different than photo albums in that the photos are made into an actual coffee table quality book with the picture right in the page, as opposed to an album or scrapbook where the pictures are placed on top of the page. It's an interesting alternative to a photo album, and the original pictures can go back to their owners. Most big box stores and chain pharmacies have this service.
Older people usually have a sluggish circulatory system, which means they are often cold. Buy your 90-year-old mother a warm, heavy blanket or quilt. To make it special, you can have it monogrammed. If you sew, you can make a homemade quilt using material from the home, perhaps from various items of clothing that was worn by family members for different occasions. If you knit or crochet, your mother may prefer a homemade afghan. Consider making her a lap quilt to keep her warm while sitting.