Made your Avatar as Round Avatar in everywhere...

1st i will show you how to make your avatar a circle avatar in memberlist.

Go to the memberlist_user_avatar template and replace all the content with this :- 

<img src="{$useravatar['image']}" style="margin-top: -20px;width: 30px; height: 30px; border-radius: 400px; transition: all 1s;text-align: center;" title="{$mybb->user['username']}" onError="this.src='{$mybb->settings['bburl']}/images/default_avatar.png';">

Go to the usercp_current_avatar template and replace all the content with this :- 

<td width="150" align="right"><img src="{$useravatar['image']}" style="width: 150px; height: 150px; border-radius: 400px; transition: all 1s;text-align: center;" alt="{$lang->avatar_mine}" title="{$lang->avatar_mine}" onError="this.src='{$mybb->settings['bburl']}/images/default_avatar.png';"></td>

if you want to make your avatar size bigger than just customize the hight and wdith in the style...

as default i have height:30px and width:30px

you can increase it.


2nd. If you want to make your avatar, round avatar in postbit then prefer this guideline.