This is a very touchy subject but one I have come across on numerous occasions and it's not always easy to talk about let alone create a moment to celebrate in a happy way the loss of a loved one.
Let's start with the time of the loss. Was it recently or some time has passed since the person died? Why this question is important is because how raw the loss is can depend on the individual, so making an honourary moment brings out different emotions in different people. The spouse or immediate family have come to your wedding to celebrate not to commemorate, so keep that in mind when creating the moment.
The subject of creating these types of moments comes when grandparents or parents have passed on, just keep in mind that these moments are sensitive in many different ways to different people so choose a commemorative moment like a song that the person loved BUT not a song played at the person's funeral.
One example of a moment I have seen had nothing to do with the reception at all, except it was mentioned that the bouquet would not be thrown, instead the bride laid the bouquet the next day on the loved one's grave. This moment was then acknowledged with a toast. Later in the evening, I played that loved one's favourite dancing song without a mention, but the family knew what the song meant to them.
Another example I have had to do for a client was to ask everyone onto the dancefloor for a commemorative dance, sort of like a slow dance for couples but it was to be played in memory of those who had passed on.
Just one this I would say in closing, make sure you ask the immediate family of the person who passed if it is ok to have a special moment in their honor.