I also look upon the faces of the ancestors I did not have the honor of knowing. I look at my grandfather who died before I was born, forever young, looking handsome and sharp in his Marine uniform. I look at my great grandparents, wearing the styles of yesteryear, dressed up for Easter Sunday, showing off a proud catch at the lake, or just lounging in the sun. Though these photos and the stories my parents told me will be the only way I may know them intellectually, I know them deeply in every cell in my body. Their blood is my blood, and it carries on through me.
As part of my daily practice, I take offerings to my ancestors. Every day, I fill a bowl with fresh water, representing new life, and place it on the altar. I light candles to represent the flame of the soul, and in doing so, rekindle their memory. I offer them incense and their favorite foods, and bring them a cup of coffee every morning to start their day.
An ancestors' altar is an easy thing to create, and can give deep roots to one's spiritual practice. For my ancestors' altar, I have chosen to only place my genetic ancestors on the altar, but I have another place where I keep photos of my memetic ancestors - friends who have died, and personal heroes of mine, people whose vision and life's work shaped my mind and influenced my spirit, and I likewise take time to commune with them. For those of you who were adopted, I'd suggest putting the photos of your adopted family on your ancestors' altar, along with any information you might have about your own genetic ancestors. One important note about the photos on your ancestors' altar: Never place the photo of someone who is currently alive on the altar. It is an insult to do so; it comes across as meaning, "Wish you were on the other side already." If you have photos you wish to use that have the images of the currently living in them, cut out only the images of the ancestors to put on your altar.
If you're troubled that you don't know too many of your ancestors, just remember: you may not know them, but they know you. Even if you don't have names and faces to put on your altar, the very act of having a place to honor them lets them know that you want them to be a part of your life, and they will bless and guide you for it. In lieu of photos, you can use photos and artifacts that represent your ancestral homeland(s) and news articles from the times and places that your ancestors were alive.
It may be true that all of your ancestors were not the nicest of people, and it may be hard to put the photos of some on there who have caused you pain during their waking life. Remember this: once dead, they have evolved to a higher state of being. The people, places and things that caused them to be hurtful are now gone, and their soul is free to return to its pure state. If you truly feel uncomfortable with putting someone's photo on your ancestors' altar, take time to commune with your other ancestors and ask them to help you heal that rift.
Honoring the ancestors is, in a sense, honoring yourself. You honor those who have shed blood, sweat, and tears for you to be here, alive, today. You honor their strength, courage, perserverence and love, of which you are the end product. Their strength is your strength, and their wisdom is your wisdom, if you will only ask them for it.