Well, one picture is max 10k, will not really add size to AD Database.
1) Get ready your picture, ours in jpg format, less than 10k, remember.
2) In Exchange 2010, launch management shell and type this command:
import-RecipientDataProperty -Identity poo -Picture -FileData (Byte] $(Get-content -path "C:\Photos\poo.jpg" -Encoding Byte -ReadCount 0))
3) Launch your Outlook 2010 and mouse over the account in your e-mail, there you go.