How do I change iMessage buddy icon?

I upgraded my iPad2 to iOS5. My Apple ID is my gmail address, (google account for email, calendar, and contacts), and it seems at first that iMessage took the icon of my google account... I changed my google account picture and my iMessage buddy icon is still my old one.

How do I change it?

Also, does anyone know how extensive interaction like this is between google accounts and apple ID accounts?