The wikia has been on a decline since the original manga completed as the new manga aren't nearly as popular. So, when it comes to information regarding Zero and Hinowa, we're lacking. You seem to be pretty new to wikia, so perhaps you edit using visual editor? In Akame's Edit dropbox, select source editor and you'll see this code string near the top:
|double image = <tabber>|-|Older= [[File:Akame main.png|250px]] |-|Younger= [[File:akameyoung.jpg|250px]]</tabber>
Make it look like this:
|double image = <tabber>|-|Older= [[File:Akame main.png|250px]] |-|Younger= [[File:akameyoung.jpg|250px]] |-|title=[[File:yourimage.png|250px]]</tabber>
Just add your own title and image to the code I added in. About the image itself, it'd be nice if you could obtain one of higher quality. One that's also just a faceshot, so that it'd fit in the infobox snuggly.