I actually called Disney about this because my entire extended family (14 of us) are going on a trip this Christmas. The trip is being paid for from the sale of my grandparents house (both have now passed away). As a surprise, we wanted to have a "leave a legacy" tile added in Disney in memory of my grandparents. This is what I was told by Disney:
You can do a text tile with 6 lines (9 characters per line). You also can pick a border - they mentioned black with white stars or mickey ears. You can leave a name and one date. You cannot use the words "in memory of" but you can say "we love you" or "we miss you". The number I called was 407-560-7235 - I had to leave a voice mail, but they did call back within a couple of days.
I have a question for others - I know the tiles are small so I'm curious as to whether you can even read the text or not. I don't want to spend the money on this if it won't even be readable. I don't imagine Disney would let you do text if you couldn't read it, but I'm interested in hearing impressions from those who have actually done a text version.
Thanks!