What about a memory lane print? You could put the places you've been and things you've done together on it. They are pretty expensive but very unique. Here's what the website says... "Your Memory Lane is a highly personalized, custom-made art print that celebrates the recipient’s memories of yesterday, joys of today, and dreams of tomorrow. This is an exceptional visual digest and keepsake gift that is as one-of-a-kind as the person, company, or group that receives it."
Here's the website: Personalized Art Prints, Birthday Gifts, Wedding Gifts, Retirement Gifts - Your Memory Lane