You have to add the image yourself manually, actually really easy to do.
Just go to your profile, click the button on the top right that says Edit My Profile Layout (your Wix profile should disappear while doing this, that is normal). Then click the button that says Avatar on the newly popped up window on the middle right side of the screen, click where it says Username on the top of the new pop-up, then type in your username and click +Add. Your avatar should now be on the profile. You can drag it anywhere you want, even re-size it. When you're done placing it, click Save on the middle right pop-up menu. Your Wix profile will now come back and your avi will be where you placed it.
Easy enough. ^^