How do you copy a contact from the SIM card to the phone in order to assign a picture to it
Although I still hope that someone else gives me a easier and quicker solution, I have found the following procedure to be a fairly quick method to accomplish what I wanted ( someone else will certainly have another idea regarding this , I'm sure ) :

I send the contact information using the Send via Gmail to my own Gmail account, press Download in the received email and choose Contacts and Phone). Since all information is present in the .vcf file attached to the mail, I can now easily create/duplicate a new contact without having to enter the name and phone number again.