How to create a custom Avatar (round profile image in sidebar)

Hi, Awesome theme. Thank you.

I’d like to use a custom image for the Avatar in the Writr theme sidebar, without going through Gravatar. I’ve tried various things – the closest I can get to it is a plugin I installed called ‘Add New Default Avatar’.

I can use all the other options in the Discussions -> Default Avatar list (eg they all display correctly – blank, other 3rd party options etc), but when I select the new custom avatar I’ve created (which shows perfectly at the backend, I get the following error message at the front end (in place of the image):

Warning: sprintf() [function.sprintf]: Too few arguments in /wp-includes/theme.php on line 900

Do you have any suggestions for overcoming this, or perhaps (instead) for drawing the round profile image from the user profile instead of Gravatar (an alternative plugin – Simple Local Avatars – lets you upload an image to the user profile, so if it grabbed it from the user profile, directly, that would be excellent)?

I can’t really link to the site, as I’ve got a coming soon plugin activated (which I don’t want to remove for now), and other than the straight theme, there’s not much to see.