Yes you can. Maximum dimensions of the picture are 500x500 pixels and the maximum size is 30 kB.
Assuming you are logged in to Pamoya Beta and you have a picture of yourself or a virtual face available on your computer.
Navigate to your account page by clicking "My account" in the main menu. Your account details and, above them, a tab bar are shown.
On the tab bar click the "Edit" tab.
To add your picture or virtual face, move to the "Upload picture" field. If you know the full path to your picture, type it in the "Upload picture" field. Alternatively click the "Browse" icon next to the "Upload picture" field. In the dialog that appears, navigate to your picture file and click "OK". The dialog will disappear and the full path to your picture will be showing in the "Upload picture" field.
Move to the bottom of the page and click "Save".
Whenever your user name is shown on the website, the picture will also be shown next to it.