Anything you want I am organising a "wishing tree" for my goddaughter for her christening (I know not a naming day per-say). Where there will be cards with ribbons attached and everyone can write a message (either a blessing or wish for the special little one) which is then tied to the tree "with love". The tree can then be planted in their yard, and the cards can be kept as special keep sakes. Reminds me of the fairy godmothers in Cinderella each giving a wish to the newborn child.

But basically yeah whatever you want. There are plenty of celebrants that do naming days and can show you books of ideas that other parents have used. Give a few a call and ask what they do they would probably be the best to offer ideas.